Energy storage system for load handling device

Abstract

The present invention is a load handling device (30) for lifting and moving one or more containers (10) stacked in a storage system comprising a grid framework (14) supporting a network of passageways arranged in a grid pattern above a stack (12) of said containers (10), the load handling device (30) comprising: i) a carrier body (32) housing a drive mechanism operatively arranged for moving the load handling device (30) on the grid framework (14); ii) a lifting device comprising a lifting drive assembly and a gripper device (39) configured in use to releasably grasp a container (10) and lift the container (10) from the stack (12) into a container receiving space (40); wherein the lifting drive assembly and / or the drive mechanism comprises at least one motor constituting an electrical load (104); iii) a rechargeable power source (100); iv) an assembly of one or more supercapacitor modules (102); characterised in that the electrical load (104) is connected across the assembly of one or more supercapacitor modules (102) and the rechargeable power source (100) is connected in parallel to the assembly of one or more supercapacitor modules (102) such that the rechargeable power source (100) is configured to power the assembly of one or more supercapacitor modules (102).

Description

Technical Field

[0001] This invention relates to the field of load handling apparatuses for processing storage containers or boxes in a store, including stacked container grids, and more particularly to energy storage systems for load handling apparatuses. Background Technology

[0002] Storage systems, including three-dimensional storage grid structures, in which storage containers / boxes are stacked on top of each other within the storage system, are known. Ocado's PCT international application, publication number WO2015 / 185628A, describes a known storage and fulfillment system in which a stack 10 of boxes or containers is arranged within a grid frame structure. The boxes or containers are accessed via a load handling device operating on tracks located atop the grid frame structure. (Appendix) Figure 1-3 This type of system is illustrated schematically. For example... Figure 1 and 2 As shown, stackable containers (referred to as boxes 10) are stacked on top of another stackable container to form a stack 12. The stack 12 is arranged in a grid frame structure 14 in a storage or manufacturing environment. The grid frame consists of a plurality of storage columns or grid columns. Each grid in the grid frame structure has at least one grid column for storing the stack of containers. Figure 1 This is a schematic 3D view of the grid frame structure 14. Figure 2 This is a top view of a stack 12 of boxes 10 arranged within a frame structure 14. Each box 10 typically holds a plurality of product items (not shown), and the product items within the box 10 can be of the same product type or different product types, depending on the application. The grid frame structure 14 includes a plurality of vertical members 16 supporting horizontal members 18, 20. A first set of parallel horizontal members 18 is positioned 25 perpendicular to a second set of parallel horizontal members 20 to form a plurality of horizontal grid structures comprising a plurality of grid cells 23 supported by the vertical members 16. Members 16, 18, 20 are typically made of metal. The boxes 10 are stacked within the grid cells 23 between members 16, 18, 20 of the grid frame structure 14, such that the grid frame structure 14 prevents horizontal movement of the stack 12 of boxes 10 and guides vertical movement of the boxes 10.

[0003] The top layer of the mesh frame structure 14 includes tracks 22 arranged in a mesh pattern, which comprises a plurality of mesh cells 23 spanning the top of the stack 12. See also Figure 3The track 22 supports a plurality of load handling devices 30. A first set 22a of the parallel tracks 22 guides the automatic load handling device 30 to move along a first direction (e.g., the X direction) across the entire top of the grid frame structure 14, while a second set 22b of the parallel tracks 22 is configured perpendicular to the first set 22a and guides the load handling device 30 to move along a second direction (e.g., the Y direction) perpendicular to the first direction. In this way, the track 22 enables the automatic load handling device 30 to move laterally in two dimensions in the horizontal XY plane, allowing the load handling device 30 to be moved to a position above any stack 12. Figure 4 and Figure 5a , Figure 5b The known load handling device 30 shown includes a vehicle body 32, which has been described in PCT International Application No. WO2015 / 019055 filed by Ocado Corporation, and is incorporated herein by reference. Each load handling device 30 covers only one grid space or grid cell 23 of the grid frame structure 14. Here, the load handling device 30 includes a wheel assembly comprising a first set of wheels 34, consisting of a pair of wheels located at the front of the vehicle body 32 and a pair of wheels 34 located at the rear of the vehicle 32, for engaging with a first set of tracks or rails to guide the device in a first direction; and a second set of wheels 36, consisting of a pair of wheels 36 located on each side of the vehicle 32, for engaging with a second set of tracks or rails to guide the device in a second direction. Each set of wheels is driven by one or more motors to enable the vehicle to move along the tracks in the X and Y directions, respectively. One or both sets of wheels can be moved vertically to lift each set of wheels off the corresponding track, thereby enabling the vehicle to move in a desired direction.

[0004] Although Figure 4 and Figure 5a , Figure 5b A load handling device occupying a single grid space is shown, wherein the container storage space is a recess inside the vehicle body. However, the present invention also covers load handling devices including a cantilever that is part of the vehicle body, wherein the container storage space is located below the cantilever.

[0005] The load handling unit 30 is equipped with a lifting device or hoisting mechanism driven by one or more motors to lift storage containers weighing up to 30 kg from above. The hoisting mechanism includes winch ropes or cables 38 wound on a reel or spool (not shown) and gripping devices 39. The lifting device includes a group of lifting ropes 38 extending vertically and connected to or near the four corners of a lifting frame 39, also referred to as a gripping device (one rope near each of the four corners of the gripping device), for releasable connection to the storage container 10. The gripping devices 39 are configured to releasably grip the top of the storage container 10 to lift it from... Figure 1 and Figure 2 The container is lifted from the stack in the storage system of the type shown.

[0006] Wheels 34 and 36 are positioned on the lower half of the outer edge of the cavity or recess (referred to as the container receiving recess). The size of the recess allows it to... Figure 5a and 5b As shown, container 10 is accommodated when it is lifted by a crane mechanism. While in the recess, the container is lifted off the lower track, allowing the vehicle to move laterally to different locations. Upon reaching the target location (e.g., another stack, an access point in a storage system, or a conveyor belt), the box or container can be lowered from the container receiving section and released from the gripper device.

[0007] Although Figure 1-3 Not shown, but the load handling device 30 is powered during operation by an on-board rechargeable power source. A common type of rechargeable power source is a battery. Examples of rechargeable batteries include lithium-ion batteries, nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion polymer batteries, thin-film batteries, and smart carbon foam-based lead-acid batteries.

[0008] The technological advantages of batteries are their high energy density, meaning a high capacity to store energy per unit mass, making them suitable for mobile applications such as load processing devices, as they store enough energy to power the device for extended periods between charges. Their low self-discharge rate allows them to retain sufficient charge for continued operation after a period of downtime. However, batteries have low power density, making them unsuitable for handling high acceleration demands and limiting how much regenerative energy they can extract from deceleration events. Furthermore, excessive battery cycling in battery tools means that some electrical energy is converted into heat, resulting in energy waste, which is also a problem in low-temperature environments.

[0009] Other disadvantages of batteries are that they are heavy, expensive, suffer from resistive power loss, have long charging times, limited charge-discharge cycle life, and degrade over time. A slow charging rate means lost operating time while the battery is charging. Limited charge-discharge cycles mean a short battery lifespan and frequent replacement.

[0010] Supercapacitors are an alternative battery technology. Supercapacitors have high power density, making them suitable for applications with high acceleration requirements (short-term high power consumption) and also capable of harvesting regenerative energy from deceleration events (short-term high power input). Supercapacitors offer advantages over batteries in that they are lighter, more efficient, charge faster, and can withstand more charge-discharge cycles with less degradation over time. Fast charging means less downtime. The main disadvantages of supercapacitors compared to batteries are their high self-discharge rate (so they may not retain enough charge to continue operating after a period of inactivity) and lower energy density.

[0011] Figure 6 This is a Ragone plot, which compares power density with energy density and shows the relative positions of different types of energy storage devices. From this plot, we can see that supercapacitors (in...) Figure 6 EDLC (electrically double-layer capacitor) batteries have low energy density but high power density, while lithium-ion batteries have relatively high energy density but relatively low power density.

[0012] Table 1 compares some properties of batteries and supercapacitors.

[0013]

[0014] Table 1: Comparison of the properties of batteries and supercapacitors

[0015] Existing load handling devices (such as those disclosed in PCT International Application No. WO2015 / 019055) have the advantage of high energy density but also suffer from all the problems of the aforementioned rechargeable batteries.

[0016] AutoStore's international patent application WO2020169474A1 discloses a container handling vehicle powered by first and second rechargeable power sources, specifically a rechargeable battery and a supercapacitor. It possesses some advantages of supercapacitors, but still suffers from the disadvantages of battery degradation and heat generation due to wasted energy.

[0017] GB2006089.3 discloses a load handling device in which the main power source is a supercapacitor, and a DC-DC converter is used to change the voltage. It has the advantages of the supercapacitor mentioned above, but since the supercapacitor is the only power source, the load handling device has the disadvantages of low energy density and high self-discharge rate.

[0018] This application claims priority to UK Patent Application No. GB2006089.3, filed on 24 April 2020, UK Patent Application No. GB2010704.1, filed on 10 July 2020, and UK Patent Application No. GB2020583.7, filed on 23 December 2020, the contents of which are incorporated herein by reference. Summary of the Invention

[0019] This invention relates to a load handling apparatus for lifting and moving one or more containers stacked in a storage system, the storage system including a grid frame supporting pathways arranged in a grid pattern above the container stack, the load handling apparatus comprising:

[0020] i) A vehicle body that encloses a drive mechanism operably configured to move a load processing device on a grid frame.

[0021] ii) A lifting device including a lifting drive assembly and a gripper, the gripper being configured in use to releasably grip a container and lift the container from the stack into a container storage space; wherein the lifting drive assembly and / or drive mechanism includes at least one motor constituting an electrical load;

[0022] iii) Rechargeable power supply;

[0023] iv) A component consisting of one or more supercapacitor modules;

[0024] The invention is characterized in that an electrical load is connected across the two ends of a component consisting of one or more supercapacitor modules, and a rechargeable power supply is connected in parallel to the component consisting of one or more supercapacitor modules such that the rechargeable power supply is configured to supply power to the component consisting of one or more supercapacitor modules.

[0025] For ease of reference, the terms "component consisting of one or more supercapacitor modules" and "supercapacitor" will be used interchangeably in the description of this invention. When referring to a supercapacitor, it should be understood that the term encompasses components consisting of supercapacitor modules connected in series and / or parallel.

[0026] A common problem with load handling devices, especially those using rechargeable batteries as the power source, is that the battery is subjected to frequent charge-discharge cycles from electrical loads, resulting from the acceleration and operation of drive components and / or mechanisms. This places the rechargeable battery under significant stress due to the increased temperature caused by the battery's internal resistance during charge-discharge cycles. These cycles can lead to premature battery aging, requiring more frequent battery replacements.

[0027] To overcome this problem, the rechargeable power supply in this invention is primarily used to power one or more supercapacitor modules, rather than directly powering the electrical load. Compared to rechargeable batteries, supercapacitors are better able to withstand charge-discharge cycles from the electrical load and are therefore able to withstand power surges during the acceleration of the load processing device on the grid. The combination of a rechargeable battery and one or more supercapacitor modules provides a hybrid system with high power density and high energy density, combining the advantages of batteries and supercapacitors. The rechargeable power supply can provide a constant current to components consisting of one or more supercapacitor modules, thereby avoiding the damaging effects of frequent charge-discharge cycles.

[0028] The advantage of this invention over existing load processing devices is that the lifespan of the rechargeable power supply is extended, thereby reducing operating costs and downtime.

[0029] The load handling device may further include a load DC-DC converter between the component consisting of one or more supercapacitor modules and the electrical load. The load DC-DC converter between the component consisting of one or more supercapacitor modules and the electrical load may be a boost converter.

[0030] The load handling device may further include a source-to-DC converter between the rechargeable power supply and the assembly consisting of one or more supercapacitor modules. The source-to-DC converter between the rechargeable power supply and the assembly consisting of one or more supercapacitor modules may be a buck converter.

[0031] The controller can be configured to alter the power supplied from a rechargeable power source to a component consisting of one or more supercapacitor modules. The controller can be configured to instruct the rechargeable power source to supply power to the component consisting of one or more supercapacitor modules when the voltage of the component is below a predetermined supercapacitor target voltage threshold. The predetermined supercapacitor target voltage threshold may be lower than the maximum rated voltage of the component consisting of one or more supercapacitor modules. The controller can be configured to instruct the rechargeable power source to supply power to the component consisting of one or more supercapacitor modules at a predetermined threshold current for achieving battery balancing. The controller can be configured to disconnect the rechargeable power source from the component consisting of one or more supercapacitor modules, causing the rechargeable power source to undergo a low-current consumption period during which no power is supplied to the component consisting of one or more supercapacitor modules.

[0032] The load handling device may further include an energy recovery circuit to transfer energy regenerated from the drive mechanism and / or lifting device components to a component consisting of one or more supercapacitor modules. This energy recovery circuit may include diodes or transistors.

[0033] A component consisting of one or more supercapacitor modules can have a lower internal impedance than a rechargeable power source.

[0034] The electrical load may include a first part and a second part, wherein the first part of the electrical load may include a powered load and the second part of the electrical load may include a non-powered load. The rechargeable power source may be configured to supply power to the non-powered load.

[0035] A component consisting of one or more supercapacitor modules can be configured as the main power supply for the load handling device, while a rechargeable power supply can be configured as an auxiliary power supply. The controller can be configured to instruct the rechargeable power supply to provide backup power to the electrical load when the voltage across the component consisting of one or more supercapacitor modules is lower than a predetermined supercapacitor voltage threshold.

[0036] Components consisting of one or more supercapacitor modules may be distributed around the outer side of the container recess within the carrier body of the load handling device, and located between the outer and inner walls of the load handling device.

[0037] A component consisting of one or more supercapacitor modules may include capacitors, supercapacitors, ultracapacitors, lithium capacitors, electrochemical double-layer capacitors, electric double-layer capacitors, pseudocapacitors, or hybrid capacitors.

[0038] Rechargeable power sources may include lithium-ion batteries, lithium-ion polymer batteries, lithium-air batteries, lithium iron batteries, lithium iron phosphate batteries, lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, sodium-ion batteries, sodium-air batteries, thin-film batteries, or smart batteries such as carbon foam-based lead-acid batteries.

[0039] Another aspect of the invention is a storage system comprising a grid frame arranged in a grid pattern supported above a stack of containers and a plurality of load processing devices as defined herein. The storage system may further include one or more supercapacitor charging stations located at grid locations above access points, wherein during rise or fall operations, one of the one or more supercapacitor charging stations charges a component on the load processing device consisting of one or more supercapacitor modules. The one or more supercapacitor charging stations may be high-rate inductive supercapacitor charging stations. A controller on the load processing device may be configured to instruct the component consisting of one or more supercapacitor modules to charge a rechargeable power source. The controller may be configured to instruct one or more supercapacitor modules to supply power to the rechargeable power source at a predetermined threshold current for achieving battery balancing. The one or more supercapacitor charging stations enable the load processing device to maintain a voltage level of the rechargeable power source above a predetermined threshold voltage for supplying power to the electrical load.

[0040] Another aspect of the invention is a fulfillment center that includes the storage system described herein. The temperature within the fulfillment center can be any of the following: an ambient temperature of 4°C or above; a refrigeration temperature of approximately 0°C to approximately 4°C; or a freezing temperature of approximately -25°C to approximately 0°C.

[0041] Connecting supercapacitors between rechargeable power sources and electrical loads allows energy storage systems to enjoy the advantages of high energy density and high power density while mitigating their disadvantages. This is especially true when the rechargeable battery is a high-energy-density battery. Supercapacitors withstand charge-discharge cycles caused by the acceleration / deceleration demands of the electrical load, protecting the battery from these cycles and thus improving battery life. Improved battery life leads to lower operating costs and less downtime because batteries no longer need to be replaced as frequently. Fewer battery cycles mean less energy loss and less effective energy wasted as heat. This is particularly important when load handling units operate in refrigerated or frozen cargo fulfillment centers where temperatures are maintained. In such cases, not only does heat release from the load handling unit represent energy waste, but greater energy consumption is required to maintain the low temperatures in the fulfillment center. Attached Figure Description

[0042] Further features of the present invention will be illustrated by the following detailed description of specific embodiments, taken in conjunction with the accompanying drawings.

[0043] in Figure 1 It is a schematic diagram based on the grid framework structure of a known system.

[0044] Figure 2 It shows the settings Figure 1A schematic top view of the stacked boxes within the frame structure shown.

[0045] Figure 3 This is a schematic diagram of a system of known load processing devices operating on a grid frame structure.

[0046] Figure 4 It is a three-dimensional schematic diagram showing a load handling device that uses a lifting device to grab a container from above.

[0047] Figure 5a yes Figure 4 A three-dimensional sectional view of the load handling device shows the container storage space of the load handling device.

[0048] Figure 5b yes Figure 4 A three-dimensional sectional view of the load handling device, showing the container housed within the container storage space of the load handling device.

[0049] Figure 6 It is an energy comparison Lagon chart, which shows the energy density and power density of different energy storage devices.

[0050] Figure 7 It is a circuit diagram showing a rechargeable power supply and a supercapacitor connected in parallel with an electrical load.

[0051] Figure 8 The circuit diagram highlights the source DC-DC converter between the rechargeable power source and the supercapacitor, as well as the load DC-DC converter between the supercapacitor and the electrical load.

[0052] Figure 9 The circuit diagrams highlight the buck and boost DC-DC converters.

[0053] Figure 10 This is a schematic diagram of a PID controller used in a boost converter.

[0054] Figure 11 The circuit diagram prominently displays the energy recovery circuit used to guide the recovered energy into the supercapacitor.

[0055] Figure 12 It is a circuit diagram that highlights a non-powered electrical load that draws power from a rechargeable power source.

[0056] Figure 13 It is a circuit diagram that shows the direction of current flow during a deceleration event.

[0057] Figure 14 It is a circuit diagram showing the direction of current flow when a rechargeable power source is charging a supercapacitor during a deceleration event.

[0058] Figure 15 It is a circuit diagram showing the direction of current flow when the load handling device is idle.

[0059] Figure 16 It is a circuit diagram showing the direction of current flow when a rechargeable power supply is charging a supercapacitor while the load processing device is idle.

[0060] Figure 17 It is a circuit diagram showing the direction of current flow in the load processing device during an acceleration event.

[0061] Figure 18 It is a circuit diagram showing the direction of current flow when the rechargeable power supply is charging the supercapacitor during an acceleration event in the load handling device.

[0062] Figure 19 The transient current caused by lowering and raising the gripper during the stacking and retrieval of storage containers is demonstrated.

[0063] Figure 20 This is a schematic diagram of the load handling device, showing the gap between the inner and outer walls of the vehicle body.

[0064] Figure 21 This is a schematic diagram of the load processing device, showing supercapacitor modules distributed in the gap between the inner and outer walls of the carrier body.

[0065] Figure 22 The charging voltage and status were compared from battery voltage measurements, manufacturer data, and battery fuel gauges.

[0066] Figure 23 This demonstrates how battery power meter readings become inaccurate after a period of continuous operation.

[0067] Figure 24 It is a circuit diagram showing a rechargeable power supply connected in parallel with an electrical load and a filter circuit.

[0068] Figure 25 It is a circuit diagram showing a rechargeable power supply connected in parallel with a power load and a filter circuit, wherein a filtered DC-DC converter is located between the filter circuit and the power load.

[0069] Figure 26 It is a circuit diagram showing a rechargeable power supply connected in parallel with a power load and a filter circuit, wherein a filtered DC-DC converter is located between the filter circuit and the power load, and a source DC-DC converter is located between the rechargeable power supply and the filter circuit.

[0070] Figure 27a A filter circuit for an RC circuit is shown.

[0071] Figure 27bThe filter circuit for the RL circuit is shown.

[0072] Figure 27c The filter circuit for the RLC circuit is shown.

[0073] Figure 27d The filtering circuit for the Butterworth filter is shown.

[0074] Figure 27e An active filter circuit using an operational amplifier is demonstrated.

[0075] Figure 28 The voltage boost of the operational amplifier is shown as plotted in relation to frequency.

[0076] Figure 29 The transient current caused by lowering and raising the gripper during the stacking and retrieval of storage containers is demonstrated.

[0077] Figure 30a This demonstrates the plotting of the entire Fourier transform of the current flowing through the rechargeable power source.

[0078] Figure 30b It demonstrates the same Fourier transform of the current flowing through a rechargeable power source in the range of 0-1000Hz and with an amplitude up to 1.

[0079] Figure 30c It demonstrates the same Fourier transform of the current flowing through a rechargeable power source in the range of 0-20Hz and with an amplitude up to 1.

[0080] Figure 30d It demonstrates the Fourier transform of the current flowing through a rechargeable power source in the 0-1Hz range.

[0081] Figure 31 A simulation model of a simple RC circuit is shown.

[0082] Figure 32a Showing with Figure 29 Same load current.

[0083] Figure 32b The current is shown when a 20Hz filter circuit is used.

[0084] Figure 32c The current is shown when a 7Hz filter circuit is used.

[0085] Figure 33a The load current and the current with a 20Hz filter circuit were compared.

[0086] Figure 33b The load current and the current with a 7Hz filter circuit were compared.

[0087] Figure 34The discharge curve of the lithium-ion battery is shown.

[0088] Figure 35 The shapes of the discharge curves of batteries and supercapacitors are shown.

[0089] Figure 36 This demonstrates the power requirements when the load processing device moves across the storage grid.

[0090] Figure 37 A simplified circuit diagram is shown, illustrating the parallel connection of supercapacitor 102 and rechargeable power supply 100.

[0091] Figure 38 The demonstration showed a multi-cell battery connected in series with a supercapacitor assembly that is connected in parallel with multiple electrical loads.

[0092] Figure 39 The circuit diagram shows the controller directing charge from a rechargeable power source to a supercapacitor.

[0093] Figure 40 The circuit diagram shows how the controller directs the recovered energy to the supercapacitor.

[0094] Figure 41 This is an enlarged view of a specific implementation of the controller and DC-DC converter.

[0095] Figure 42 The supercapacitor protection circuit was demonstrated. Detailed Implementation

[0096] A rechargeable power source configured to supply power to a component consisting of one or more supercapacitor modules.

[0097] Figure 7 This is a circuit diagram showing a rechargeable power supply 100 connected in parallel with a supercapacitor 102 and an electrical load 104. The electrical load 104 may include one or more motors that move a vehicle along a track in the X and Y directions via groups of drive wheels 34 and 36, and / or one or more motors that drive a lifting device or hoisting mechanism to lift the storage container from above. The supercapacitor 102 is connected between the rechargeable power supply 100 and the electrical load 104, allowing the rechargeable power supply to provide power to or receive power from the supercapacitor, and the supercapacitor to provide power to or receive power from the electrical load.

[0098] For ease of display, Figure 7 The circuit diagram shows the rechargeable power supply 100 as a single battery cell and the supercapacitor 102 as a single supercapacitor. It should be understood that the rechargeable power supply is not limited to a battery, and a battery may include a component consisting of one or more battery cells, not just a single battery cell.

[0099] Similarly, supercapacitor 102 may include a component consisting of one or more supercapacitor modules, rather than just a single supercapacitor module.

[0100] DC-DC converter

[0101] The circuit may additionally include a source-to-DC converter 108 located between the rechargeable power supply 100 and the supercapacitor 102. The purpose of the source-to-DC converter is to convert the voltage across the rechargeable power supply to a different voltage across the supercapacitor.

[0102] The source-to-DC converter 108 between the rechargeable power supply 100 and the supercapacitor 102 may include a boost converter or a buck converter. Preferably, the source-to-DC converter 108 between the rechargeable power supply 100 and the supercapacitor 102 may include a boost converter. The advantage of a higher voltage across the supercapacitor is that the supercapacitor can store more energy. In addition, the higher voltage (and thus the lower current) results in lower impedance power loss (P = I^2 R) and therefore reduces the amount of effective energy converted into heat.

[0103] The circuit may additionally include a load DC-DC converter 110 located between the supercapacitor 102 and the electrical load 104. The purpose of the load DC-DC converter 108 between the rechargeable power supply 100 and the supercapacitor 102 is to convert the voltage across the supercapacitor to a different voltage across the electrical load.

[0104] The load DC-DC converter 110 between the supercapacitor 102 and the power load 104 may include a boost converter or a buck converter.

[0105] Figure 8 This is a circuit diagram showing the source DC-DC converter 108 between the rechargeable power supply 100 and the supercapacitor 102, and the load DC-DC converter 110 between the supercapacitor 102 and the electrical load 104. It should be understood that, although... Figure 8 Two DC-DC converters are shown, but the present invention covers circuits that include a source DC-DC converter 108 but not a load DC-DC converter 110, and circuits that include a load DC-DC converter 110 but not a source DC-DC converter 108.

[0106] Preferably, the source-to-DC converter 108 between the rechargeable power supply 100 and the supercapacitor 102 is a digitally controlled boost converter, and the source-to-DC converter 110 between the supercapacitor 102 and the power load 104 is a buck converter. Figure 9This is a circuit diagram illustrating the case where the source DC-DC converter 108 between the rechargeable power supply 100 and the supercapacitor 102 is a boost converter, and the load DC-DC converter 110 between the supercapacitor 102 and the electrical load 104 is a buck converter. The controller 114 can be used to minimize the current from the rechargeable power supply while keeping the supercapacitor voltage within the desired range.

[0107] The source-to-DC converter 108 between the rechargeable power supply 100 and the supercapacitor 102 is a boost converter, which has the advantage that the voltage of the supercapacitor will never drop below the voltage of the rechargeable power supply. Therefore, the load DC-DC converter can power the electrical load 104 via a simple buck converter. Energy recovered from the deceleration time can be directed to the supercapacitor via the energy recovery circuit 112. The circuit can be as simple as a power diode controlling the current flow from the electrical load to the supercapacitor.

[0108] Controlling the charging of supercapacitors

[0109] One important issue to consider is how to control the state of charge of the supercapacitor. If the supercapacitor is fully charged, then the recovered energy after a deceleration event will not be able to be stored in the supercapacitor. In this case, the recovered energy will need to be directed to a rechargeable power source (which would lead to battery aging if the rechargeable power source is a battery) or dissipated as heat.

[0110] Figure 10 A possible specific implementation of controller 114 as a PID controller is shown. One option for controller 114 is to allow the rechargeable power supply to charge the supercapacitor only when the supercapacitor's charge is below a predetermined supercapacitor target voltage threshold. This can be achieved by measuring the voltage Vc across the supercapacitor and allowing the rechargeable power supply to charge the supercapacitor when the supercapacitor voltage is below the predetermined supercapacitor target voltage threshold. The predetermined supercapacitor target voltage threshold Vr is compared with the instantaneous supercapacitor voltage Vc, and controller 114 adjusts its output accordingly.

[0111] Energy recovery

[0112] During a deceleration event, kinetic energy can be recovered from the deceleration of the load handling device and stored in a supercapacitor for later use.

[0113] The energy storage system of the load handling device must be able to receive power from the drive mechanism during deceleration events, in which the load handling device decelerates from its maximum speed in the X or Y direction until it comes to a stop at a different grid position. The drive mechanism may include one or more electric motors, which act as generators during deceleration events, converting the kinetic energy of the load handling device into electrical energy, which can be stored in a supercapacitor for later use.

[0114] The energy storage system of the load handling unit must be able to receive power from the lifting mechanism during deceleration events, when the gripper is lowered to a lower vertical position within the storage grid. As the gripper is lowered, potential energy from its higher initial vertical position is converted into kinetic energy. The lifting drive assembly may include one or more electric motors, which act as generators during deceleration events, converting the kinetic energy of the load handling unit into electrical energy, which can then be stored in a supercapacitor for later use.

[0115] It should be understood that during reduced operation, more energy can be recovered when the gripper grasps the storage container because the mass of the storage container means that more energy from the higher vertical initial position of the gripper and the storage container can be recovered.

[0116] Through such Figure 11 The energy recovery circuit 112 shown transfers recovered energy into the supercapacitor 102. The purpose of the energy recovery circuit 112 is to direct current into the supercapacitor 102. This is beneficial because the recovered energy directed into the rechargeable power source increases the number of charge-discharge cycles and, if the rechargeable power source is a battery, accelerates battery aging. The energy recovery circuit may include one or more diodes or transistors.

[0117] A component consisting of one or more supercapacitor modules can have a lower internal resistance than a rechargeable power source, thereby ensuring that recovered energy is directed into the supercapacitor rather than into the rechargeable power source.

[0118] The supercapacitor is designed to be large enough to receive and store recovered energy.

[0119] A predetermined target voltage threshold for the supercapacitor can be selected, making it lower than the supercapacitor's maximum rated voltage, and ensuring that the voltage difference between the predetermined target voltage threshold and the supercapacitor's maximum rated voltage is sufficient for the supercapacitor to receive energy recovered from one or more deceleration events. Additionally, the rated power of the supercapacitor can be selected such that it is sufficient to receive power from deceleration events.

[0120] The dimensions of the supercapacitor module assembly can be designed such that the voltage difference between a predetermined supercapacitor target voltage threshold and the supercapacitor's maximum rated voltage is sufficient to receive and store energy from a deceleration event.

[0121] Alternatively, the dimensions of the supercapacitor module assembly can be designed such that the voltage difference between a predetermined supercapacitor target voltage threshold and the supercapacitor's maximum rated voltage is sufficient to receive and store energy from a plurality of deceleration events. For example, if a load handling device needs to move along the Y direction to different grid cells and stack storage containers, this operation includes four acceleration / deceleration events: accelerating to maximum speed along the Y direction (acceleration event); decelerating along the Y direction to dock above the target grid cell (deceleration event); lowering the gripper and storage container from the load handling device's container storage space to a lower vertical position to stack the storage container (deceleration event); and raising the gripper back to the load handling device (acceleration event). There are two consecutive deceleration events in this time sequence. Dimensioning the assembly, composed of one or more supercapacitor modules, such that the voltage difference between a predetermined supercapacitor target voltage threshold and the supercapacitor's maximum rated voltage is sufficient to receive and store energy from these two deceleration events means that the supercapacitor itself can be used for this operation, thereby reducing the number of power cycles required for the rechargeable power supply and potentially extending its lifespan. Overall, the energy capacity of a supercapacitor is sufficient to handle more than a typical deceleration event, which is an advantage, as the rechargeable power supply does not need to receive energy from acceleration events during normal operation. Reversing the direction of current through a rechargeable power supply can accelerate the aging process and reduce its lifespan, especially when the rechargeable power supply is a battery.

[0122] Designing the supercapacitor to be sized such that the voltage difference between the predetermined target voltage threshold and the supercapacitor's maximum rated voltage is sufficient to receive and store energy from multiple deceleration events is advantageous. This ensures that even in the event of unexpected high deceleration events, the energy flow between the rechargeable power source and the supercapacitor remains in only one direction during normal grid operation. The supercapacitor effectively implements charge-discharge cycles from acceleration / deceleration events, protecting the rechargeable power source from the aging effects of these cycles. The rechargeable power source only needs to provide a constant energy "top-up" to the supercapacitor at low power, without undergoing charge-discharge cycles from all acceleration / deceleration events as would occur if the rechargeable power source were the sole power source in the energy storage system. An additional advantage of this is the greater ease of providing a smooth and constant current distribution to the rechargeable power source.

[0123] If the source-to-DC converter 108 between the rechargeable power supply and the supercapacitor is a boost converter, then the predetermined target voltage threshold for the supercapacitor can be higher than the voltage of the rechargeable power supply. The advantage of this is that the supercapacitor 102 can store more capacity, since energy storage capacity is proportional to the square of the voltage.

[0124] One option is to set the minimum voltage of the supercapacitor to be no lower than the voltage of the rechargeable power supply. The advantage of this is that the load DC-DC converter 110 can be a simple buck converter powering the electrical load 104. Additionally, if the voltage of the supercapacitor is not lower than the voltage across the electrical load, the energy recovery circuit 112 can remain as simple as a power diode. The disadvantage of this option is that only a portion of the supercapacitor's voltage range can be utilized.

[0125] Allowing the supercapacitor's voltage to drop below the rechargeable power supply's voltage allows for wider utilization of the supercapacitor, but it also necessitates a more complex electronic structure between the rechargeable power supply and the supercapacitor, rather than a simple boost converter. Furthermore, if the supercapacitor's voltage drops below the voltage across the electrical load, the energy recovery circuit 112 needs to become more complex to prevent supercapacitor overvoltage. Exceeding the supercapacitor's maximum rated voltage will reduce the unit's operating life and eventually lead to failure.

[0126] For example, if both the voltage of the rechargeable power supply and the power load are nominally 48V, then the predetermined overvoltage target voltage threshold can be set to 60V. A supercapacitor can be selected such that its maximum rated voltage is 72V, ensuring sufficient energy storage capacity to store energy recovered from deceleration events. If the supercapacitor voltage is below 60V, the controller will allow the rechargeable power supply to charge the supercapacitor. If the supercapacitor voltage is above 60V, the controller 114 will not allow the rechargeable power supply to charge the supercapacitor. The supercapacitor will provide energy for acceleration events until the voltage drops below 60V, after which the controller will allow the rechargeable power supply to recharge the supercapacitor. To simplify the required electronics in the source DC-DC converter 108 and the energy recovery circuit 112, the supercapacitor 102 can be limited to operate above a minimum operating voltage of 48V.

[0127] Non-power electrical loads

[0128] Electrical loads can include both powered and non-powered electrical loads. Powered electrical loads are those required by drive mechanisms and / or lifting drive components and change based on the movement of the load handling device. Non-powered electrical loads are electrical loads used for any function other than the movement of the load handling device, and may include, for example, power for communicating with the storage grid control system. These non-powered electrical loads always exist independently of the movement of the load handling device. Figure 12 The circuit diagram of the non-powered electrical load 106 is shown. The non-powered electrical load can be powered by the rechargeable power supply 100.

[0129] The supercapacitor size is designed to accelerate events.

[0130] The load handling unit's energy storage system must be able to power the drive mechanism to enable the load handling unit to move along the X and Y directions on the grid. Movement along the X or Y direction includes acceleration events where the load handling unit starts docking and accelerates until it reaches its maximum speed, and subsequent deceleration events where the load handling unit decelerates from its maximum speed until it docks at different grid positions. Each acceleration event is generally followed by a deceleration event.

[0131] The energy storage system of the load handling unit must be able to power the lifting drive assembly to raise and lower the gripper to retrieve or stack storage containers. Lifting operations consist of a deceleration event where the gripper lowers from the load handling unit to a lower vertical position within the grid frame, followed by an acceleration event where the gripper grasps the storage container and lifts it vertically upwards into the container storage space within the load handling unit. Similarly, stacking operations consist of a lowering event where the gripper grasps the storage container from the load handling unit to a lower vertical position within the grid frame for stacking the storage container, followed by an acceleration event where the gripper lifts it vertically upwards into the load handling unit. Each deceleration event is generally followed by an acceleration event.

[0132] The size of a component consisting of supercapacitor modules can be designed such that the rated power is sufficient to power an acceleration event.

[0133] Alternatively, the size of a component consisting of supercapacitor modules can be designed such that its rated power is sufficient to power multiple acceleration events. For example, if a load handling device needs to retrieve a storage container and move it along the X direction to a different grid cell, this operation involves four acceleration / deceleration events: lowering the gripper (deceleration event); raising the gripper and storage container to place the storage container into the container storage space (acceleration event); accelerating to maximum speed along the X direction (acceleration event); and decelerating to dock above the target grid cell (deceleration event). There are two consecutive acceleration events in this sequence. Designing a component consisting of one or more supercapacitor modules such that its rated power is sufficient to power two acceleration events means that the supercapacitor itself can be used for this operation, thereby reducing the number of power cycles required by the rechargeable power supply and potentially extending its lifespan. Overall, the supercapacitor's power being sufficient for more than one typical acceleration event is an advantage, so that the rechargeable power supply does not need to power acceleration events during normal operation, but only needs to replenish the supercapacitor when the charge drops below a specified level. If there is an unexpected high acceleration, the rechargeable power supply will still be spared from power cycling.

[0134] The size of a supercapacitor can be designed to have sufficient power and available energy to complete acceleration events that require the most energy, such as moving along the X or Y direction across the entire storage grid.

[0135] Circuit operation

[0136] Figure 13-18 This diagram illustrates the circuitry of the load handling device under different conditions (during deceleration, idle, and acceleration). In each case, the circuitry is shown when the rechargeable power supply is charging the supercapacitor and when it is not. The arrows in the diagram indicate the direction of current flow.

[0137] Figure 13 The circuitry demonstrates the operation of the load handling device during a deceleration event. Energy is recovered from the electrical load 104 (e.g., from a drive or lifting mechanism) and directed by the energy recovery circuit 112 to the supercapacitor 102. The rechargeable power supply 100 supplies power to the non-powered electrical load 106. The circuit diagram actually shows two separate circuits.

[0138] Figure 14 This demonstrates the operation of the circuitry when the load handling device is undergoing a deceleration event and the rechargeable power supply is charging the supercapacitor. Energy is recovered from the electrical load 104 (e.g., from a drive mechanism or lifting mechanism) and directed by the energy recovery circuit 112 to the supercapacitor 102. The rechargeable power supply 100 supplies power to the supercapacitor 102 and the non-powered electrical load 106. For this operation to be possible, the supercapacitor's rated power must be sufficient to receive power from both the energy recovery circuit and the rechargeable power supply.

[0139] Figure 15 The operation of the circuitry when the load handling device is idle is demonstrated. The rechargeable power supply 100 supplies power to the non-powered electrical load 106. The source DC-DC converter 108 can be disconnected, so that no power is supplied to the supercapacitor 102.

[0140] Figure 16 The circuit operation is illustrated when the load handling device is idle and the rechargeable power supply is charging the supercapacitor. The rechargeable power supply 100 supplies power to the non-powered electrical load 106 and the supercapacitor 102. The load DC-DC converter 110 can be disconnected, so that no power is supplied to the electrical load 104. The circuit can have an active mode, in which the load handling device urgently needs acceleration, in which case the load DC-DC converter 110 can be connected to prepare to supply power to the electrical load 104.

[0141] Figure 17 The circuitry demonstrates the operation of the load handling device during an acceleration event. Supercapacitor 102 supplies power to electrical load 104 (e.g., from a drive mechanism or lifting mechanism). Rechargeable power supply 100 supplies power to non-powered electrical load 106. The circuit diagram actually shows two separate circuits.

[0142] Figure 18The circuit operates when the load handling device is undergoing an acceleration event and the rechargeable power supply is charging the supercapacitor. The supercapacitor 102 supplies power to the electrical load 104 (e.g., from a drive mechanism or lifting mechanism). The rechargeable power supply 100 supplies power to the non-powered electrical load 106. If the impedance of the electrical load 104 is lower than the impedance of the supercapacitor 102, then the rechargeable power supply 100 can supply power to the supercapacitor 102; otherwise, the rechargeable power supply can supply power to the electrical load.

[0143] Rechargeable power supplies provide average current

[0144] One of the main advantages of using supercapacitors to power load handling devices is that the supercapacitor undergoes charge-discharge cycles, rather than a rechargeable power source. A rechargeable power source carries an average current, not cycles.

[0145] Figure 19 This is a diagram illustrating the principles of supercapacitor use. It plots the current flowing through the electrical load over the time it takes for a 15kg supercapacitor to be lowered to a depth of 12 grid cells in a grid storage system and then raised. The solid lines represent the current supplied to / recovered from the lift-drive assembly (electrical load). The diagram first shows the deceleration event, in which the lift-drive assembly lowers the supercapacitor from the container housing of the load handling device into the grid, while kinetic energy is recovered from the supercapacitor and converted into electrical energy by the lift-drive assembly (negative current). Next, it shows the acceleration event, in which energy is supplied to the lift-drive assembly to raise the supercapacitor to the top of the grid and place it in the container housing of the load handling device (positive current). If only a rechargeable power supply is used to power the lift-drive assembly of the load handling device, the rechargeable power supply will experience transient currents of up to 23 amps (deceleration) and 14 amps (acceleration). The surges and transient nature of such currents, combined with numerous partial charge-discharge cycles, accelerate the aging of the rechargeable power supply. If the rechargeable power source is a battery, then this effect is even more certain.

[0146] Figure 19 The dashed line represents the average current required by the electrical load. The average current is approximately 1 ampere (decelerated). If the supercapacitor placed between the rechargeable power supply and the electrical load acts as a perfect filter, it will receive the entire current signal, including all transients, while the rechargeable power supply will withstand an average current of 1 ampere. Removing transients means the rechargeable power supply does not need to undergo any charge-discharge cycles, significantly extending its expected lifespan. Supercapacitors are well-suited for handling transients in current because they have high power density and do not age prematurely due to numerous charge-discharge cycles.

[0147] Using components consisting of one or more supercapacitor modules also improves the efficiency of energy storage systems. Power loss is proportional to the square of the current, therefore, smaller currents in rechargeable power supplies result in significantly reduced power loss. (As mentioned above...) Figure 19 In the scenario shown, the heat generated within the rechargeable power supply during the process of lowering a 15kg storage container to a depth of 12 grid cells and then raising it is 230 J / Ohm. Using a component consisting of one or more supercapacitor modules to power the lowering and raising of the storage container would reduce this heat generation in the rechargeable power supply to 2.8 J / Ohm (calculated using average current). This reduces the generated heat by 1 / 82nd.

[0148] In addition to improving efficiency, reducing power loss is particularly important when load handling units process refrigerated or frozen goods in fulfillment centers and when fulfillment centers need to maintain low temperatures. The heat generated by the rechargeable power supply in the load handling unit means that the cooling system of the fulfillment center needs to expend more energy to maintain the required low temperature.

[0149] Supercapacitors serve as the main power source, with rechargeable power supplies providing auxiliary power.

[0150] In one specific embodiment of the invention, the supercapacitor 102 can be used as the main power source for the load processing device, supplemented by a rechargeable power supply 100. This allows the load processing device to operate using the supercapacitor as the main power source and thus benefit from the advantage of rapid charging of the supercapacitor at a supercapacitor charging station.

[0151] When the rechargeable power source is a battery, the relatively long charging time can be several hours, representing a significant downtime during which load handling units will remain inactive or non-operational on the grid structure. If a large number of load handling units are operating on the grid to fulfill customer orders within a given time period, the prolonged idleness of one or more load handling units negatively impacts the ability of fulfillment centers or distribution warehouses to fulfill orders on time. This is particularly true in logistics systems where load handling units are used to provide home delivery of goods to customers' residences after receiving orders. In this case, delivery information containing delivery addresses is used by online retailers (such as Amazon and Occidental UK) to deliver goods to customers' delivery addresses. To mitigate such issues, online retailers (such as Occidental UK) provide load handling units operating on the grid as a buffer to accommodate load handling units remaining idle for charging. In extreme cases, order delivery periods are extended to accommodate this downtime. Using supercapacitors as the main power source solves the drawbacks of slow battery charging, reduces downtime, and contributes to efficient customer order fulfillment.

[0152] Batteries based on lithium-ion, nickel-cadmium, nickel-metal hydride, or lithium-ion polymer battery technologies rely on chemical reactions to store electrical energy. The effectiveness of these batteries decreases after repeated charging due to damage to the lithium-ion cells, thus reducing their ability to store charge over time.

[0153] Charging stations for supercapacitors typically operate at higher currents than battery charging stations because supercapacitors have a higher power density and can therefore tolerate higher charging power (they also have the advantage of fast charging). Storage grids can be equipped with two types of charging stations: one with a higher rated power / higher current for charging supercapacitors, and one with a lower rated power / lower current for charging rechargeable power sources.

[0154] The load handling device can be controlled by a control system that monitors the charging level of the energy storage system. This control system determines whether the load handling device's energy storage system needs charging and directs the load handling device to a charging station if the charging level drops below a predetermined threshold. Using dual power supplies, the control system can determine whether the supercapacitor or rechargeable power source needs charging, select an appropriate charging station, and direct the load handling device to the selected charging station on the storage grid.

[0155] Alternatively, a single type of combined charging station can be provided, which can be configured to provide either low current (for slow charging of rechargeable power sources) or high current (for fast charging of supercapacitors). The control system determines when the energy storage system of the load handling unit needs charging, determines whether the supercapacitor or rechargeable power source needs to be charged, selects an appropriate combined charging station, guides the load handling unit to the selected charging station on the storage grid, and determines whether a high or low charging current should be used.

[0156] The charging station can be an inductive wireless charging station.

[0157] In the current specific embodiment of the present invention, the component consisting of one or more supercapacitor modules is the main power source; therefore, most charging will be fast charging of the component consisting of one or more supercapacitor modules. The rechargeable power source only needs to be charged occasionally when the power is depleted.

[0158] Rechargeable power supply provides auxiliary power after grid downtime.

[0159] Sometimes the entire storage system needs to be offline for short periods (known as "grid downtime") for maintenance activities or to resolve issues with load processors. This can cause problems if the load processors are powered solely by supercapacitors, which act as the main power source. Supercapacitors have high self-discharge rates; typically, after an hour of inactivity, a supercapacitor will partially discharge below a predetermined threshold voltage required to power the electrical load. At this point, the supercapacitor will no longer be able to provide the power needed to move the load processors across the storage grid. After the grid downtime ends and the load processors restart, they may not be able to return to the charging station on their own power. They will need to be retrieved from their location and sent to the charging station before they become operational again, extending the grid downtime period.

[0160] This problem is addressed by using a rechargeable power source as a backup power source when the supercapacitor, which serves as the primary power source, has discharged, especially when the rechargeable power source is a battery. Batteries have the advantage of a low self-discharge rate, so they do not discharge significantly after periods of inactivity. When the supercapacitor's state of charge has dropped to a level where it cannot provide the required power after grid downtime for maintenance activities, the rechargeable power source will be able to provide backup power to the electrical load, enabling the load handling equipment to move.

[0161] The load handling device can switch to operation with power from a rechargeable power source when the supercapacitor 102 is partially or fully discharged, thereby avoiding the risk of the load handling device running out of power and remaining on the grid, which would require downtime to retrieve the load handling device and send it to the charging station.

[0162] Supercapacitors in low-temperature environments

[0163] Supercapacitors outperform battery technology in low-temperature environments, making load processing devices powered by supercapacitors particularly suitable for these operating conditions.

[0164] Load handling units can operate in fulfillment centers that maintain low temperatures, such as when fulfilling customer orders for refrigerated or frozen goods. Not only does the heat generated by the load handling unit's energy storage system represent a waste of energy, but even more energy must be consumed to keep the fulfillment center at a low temperature.

[0165] Table 2 shows the performance of lithium-ion batteries that power load processing devices on a grid frame structure.

[0166]

[0167] Table 2: Battery performance of lithium-ion batteries in the load processing device.

[0168] Typically, a lithium-ion battery requires 15 minutes of charging after every 4 hours of discharge. During a 4-hour operation on a grid-frame structure, the power load reaches a peak of 600W, decreasing to 96W at idle. This power consumption is due to communication between the controller (control unit) in the load handling unit and the central control system. The average power consumption of the load is 400W over the entire 4-hour period, corresponding to 100Wh of energy consumed per operating cycle. The energy storage system on the load handling unit will need to store at least 100Wh of energy upon full charge. Lithium-ion batteries have a lifespan of 3 years at ambient temperature (10°C - 30°C) and 0.5 years at refrigerated temperature (0.5°C).

[0169] Unlike lithium-ion batteries, supercapacitors do not suffer from the shortened lifespan caused by low-temperature operation. Supercapacitors are typically rated for operation temperatures as low as -40°C without any performance degradation.

[0170] Load handling units may need to operate in low-temperature environments when storage systems are used for refrigerated or frozen goods. Specifically, the storage system may be located in a fulfillment center with refrigerated or frozen environments, and the load handling unit will need to be able to operate in this environment. Freezing temperatures cover a range of approximately -25°C to approximately 0°C, while refrigeration temperatures cover a range of approximately -0°C to approximately 4°C. Therefore, supercapacitors are typically operating at their rated operating temperatures in refrigerated or frozen environments.

[0171] Table 3 shows the calculated charging current applied at 48 volts to a commercially available supercapacitor module with an initial charge capacity of 100Wh at different desired charging and discharging times, as an example. The average power consumption over 4 hours for lithium-ion batteries, as shown in Table 2, is assumed to be 400W. The charging times shown in the tables for supercapacitors (from 5 to 30 seconds) are much faster than those for lithium-ion batteries (typically 15 minutes).

[0172] Table 4 shows the equivalent energy and equivalent depth of discharge (DOD) of the supercapacitor at different discharge times, assuming an initial charge of 100Wh. The lithium-ion battery in the load handling device shown in Table 2 consumes an average of 400W of power. To obtain the same power from a supercapacitor initially charged to provide 100Wh of energy, the supercapacitor would need to be fully discharged every 15 minutes, achieving a DOD of 100%. Similarly, a 5-minute discharge time represents a 33% DOD, equivalent to 33Wh of energy.

[0173] Based on the operation of the load processing device on the lattice frame structure and the power consumed by the load processing device in performing tasks on the lattice frame structure, short energy pulses can be sent to the supercapacitor module to replenish the supercapacitor module with enough power to enable the load processing device to operate by accessing one or more supercapacitor charging stations. The charging time of the supercapacitor module is only a fraction of the time spent performing tasks on the lattice frame structure. Due to the relatively short charging time (in seconds) and the fact that supercapacitors can tolerate multiple charge cycles, the load processing device can access charging stations multiple times during operation on the lattice frame structure. For example, a supercapacitor can cycle at 100% depth of discharge more than 290,000 times, which is equivalent to approximately 8 years of operating life, far exceeding the operating life of a typical battery.

[0174]

[0175] Table 3: Charging current at different charging and discharging times at 48 volts

[0176]

[0177] Table 4: Energy used (Wh) when the average power consumption is 400W.

[0178] Distribute supercapacitor modules to reduce the center of mass of the load handling unit

[0179] In one specific embodiment of the present invention, the load processing device occupies only one grid space or grid cell of the grid frame structure (e.g., ...). Figure 4 and Figure 5a , Figure 5b (As shown). Its advantage is that a greater number of load processing devices can be active on the grid at any given time. However, Figure 5a and Figure 5b The load handling device shown, with a container receiving recess 40 at the bottom, includes a lifting drive assembly, a drive mechanism, and an energy storage system located above the container receiving recess. A disadvantage of this arrangement is that the center of mass of the load handling device is relatively high, negatively impacting its stability.

[0180] To reduce the center of mass and thus improve the stability of the load handling device, one or more supercapacitor modules may be distributed around the outside of the container housing recess. Figure 20 A load handling device 30 is shown, which includes a container receiving recess 40 located within a carrier body 32. The carrier body 32 includes four outer walls 42 located on four sides of the load handling device 30 and four inner walls 44 forming the inner surface of the carrier body, in which the container receiving recess 40 is located. A gap 46 exists between the inner walls 44 and the outer walls 42 of the carrier body.

[0181] Figure 21 This demonstrates how the supercapacitor module 48 is arranged within the gap 46 between the inner wall 44 and the outer wall 42. It should be understood that the center of mass of the load handling device is lowered because the supercapacitor module 48 is placed at a lower position within the load handling device. Without this arrangement, the assembly consisting of one or more supercapacitor modules would otherwise be placed in the upper part of the load handling device, above the container receiving recess 40. The lower center of mass makes the load handling device more stable.

[0182] The stability of the load handling unit is an important consideration. An unstable load handling unit may be at risk of tipping over, requiring grid downtime to retrieve the load handling unit and return it to an upright position.

[0183] Recalibrate the battery state-of-charge calculation using the low-current consumption period.

[0184] Figure 22 The charge-discharge curves of the lithium-ion battery in the load processing device are displayed, with the state of charge (SOC) plotted against the battery voltage. Data was measured after the load processing device operated on the grid for one day. Three sets of data were plotted: i) SOC obtained by measuring the battery voltage at a series of different battery current values; ii) open-circuit voltage curves from the battery manufacturer's datasheet; and iii) estimated SOC from the battery fuel gauge at a series of different battery current values. Because i) and iii) were measured at a series of different battery current values, there are several sets of data, not just a single line. Data point ii) is located at a single current (open-circuit voltage corresponds to zero current), so there is only one data line. Figure 22 It can be seen that all three data groups are aligned; the grouping of data points that align i) the SOC obtained by measuring voltage and iii) the estimated SOC from the battery fuel gauge with the manufacturer's data were measured at zero current. This alignment indicates that the battery fuel gauge accurately measures the battery's true SOC.

[0185] Battery capacity meters estimate State of Charge (SOC) based on the coulomb counting method. This method measures the current drawn from and supplied to the battery and integrates it with time to estimate the remaining usable capacity. The advantage of coulomb counting is its simplicity and direct implementation; however, because current measurement cannot be perfectly accurate, the method is susceptible to drift over time if the measurement is not recalibrated to a standard point.

[0186] Figure 23 The charge-discharge curves of the lithium-ion battery in the load processing device are shown, in comparison with... Figure 23A similar approach was used to plot the State of Charge (SOC) for battery voltage. Data was measured after the load processing device had been running continuously on the grid for several days. Three sets of data were plotted again: i) SOC obtained by measuring battery voltage at a batch of different battery current values, ii) open-circuit voltage curves from battery manufacturer datasheets, and iii) estimated SOC from the battery fuel gauge at a batch of different battery current values. Figure 23 It can be seen that the SOC obtained by measuring the voltage is aligned with the manufacturer's data along the charging curve. However, the estimated SOC from the battery fuel gauge is not aligned with the manufacturer's data. There is a discrepancy between the battery fuel gauge SOC reading and the actual SOC. Figure 23 The gap indicated by the arrow is as high as 15-20% of the SOC, indicating that the battery fuel gauge is no longer accurately reporting the battery's true SOC, but rather is actually overestimating the available SOC. This is true for both the charging and discharging curves.

[0187] This inaccuracy in the battery fuel gauge's estimated State of Charge (SOC) is a problem because SOC is used by the control system to determine when to recharge the battery. For example, the control system might instruct the load handler to proceed to a charging station when the SOC has already dropped below 30%. When the fuel gauge indicates the SOC is below 30%, the actual SOC might be as low as 10%-15%. This is problematic because it increases the risk that the load handler will run out of battery power before reaching the charging station. In such cases, it might be necessary to stop the grid operation when retrieving the load handler and delivering it to the charging station.

[0188] The inaccuracy of the battery fuel gauge's estimated SOC gradually increases with operating time. After one day of operation on the grid, the battery fuel gauge accurately reports the SOC (see...). Figure 22 However, after working continuously on the grid for several days, the battery power meter stopped reporting SOC accurately.

[0189] The problem here is that battery capacity is easily underestimated due to inaccuracies in tracking transient current peaks. If current transients occur at a higher frequency than the battery fuel gauge measures, the peaks will not be accurately captured. Underestimating the current supplied by the battery leads to an overestimation of the remaining usable capacity, which explains why the estimated SOC from the battery fuel gauge shifts upward over time. Even a small underestimation of the current supplied by the battery accumulates over time and causes a shift between the fuel gauge's estimated SOC and the actual SOC.

[0190] This issue can be addressed by recalibrating the fuel gauge to allow the battery cell to experience a low-current-consumption period, during which the battery discharges zero current or as little current as possible. This rest period gives the fuel gauge an opportunity to recalibrate the estimated state of charge (SOC) and will make it easier to reduce 'offset'.

[0191] Recalibration can be performed by checking whether the battery fuel gauge's estimated SOC at known voltage and current matches the expected SOC at the same voltage and current in the manufacturer's datasheet. This can be done for any known current, but zero current is more convenient because the open-circuit voltage profile is readily available from the battery manufacturer. When the battery current is zero, the expected SOC can be read from the manufacturer's OCV profile for a given voltage. Therefore, the battery fuel gauge can identify the difference between the expected SOC and the fuel gauge's estimated SOC and recalibrate by updating the fuel gauge's estimated SOC to match the expected SOC.

[0192] Another method for predicting SOC is voltage measurement, rather than coulomb counting. However, because battery voltage drops sharply over time due to battery discharge, even small changes in voltage correspond to large changes in SOC. This means that voltage-based SOC predictions are not always accurate. Assuming calibration issues can be resolved, coulomb counting is a better method for predicting SOC than voltage measurement.

[0193] A load handling device comprising a component consisting of one or more supercapacitor modules and a battery energy storage system can better utilize dual power sources by using the supercapacitor for only a short period. This allows the battery to have a low-current consumption period with zero or low current demand, during which the battery fuel gauge can be recalibrated and thus display more accurate SOC measurements.

[0194] While zero current consumption is ideal for low-current-consumption periods to recalibrate the battery fuel gauge to the manufacturer's open-circuit voltage profile, it may not be achievable in practice. Therefore, current consumption should be kept as low as possible. Low-current-consumption periods can be achieved by periodically disconnecting the battery from a component consisting of one or more supercapacitor modules, ensuring that no power is supplied to the supercapacitors. "Periodic disconnection" refers to a short disconnection at predetermined intervals (e.g., every four hours).

[0195] Battery SOC Balance

[0196] The individual cells in a battery pack naturally have slightly different capacities, and therefore may be in different states of charge during charge-discharge cycles. Capacity differences may be due to manufacturing variations, assembly variations (e.g., cells from one manufacturing batch being mixed with cells from other batches), battery aging, impurities, or environmental exposure (e.g., some cells may be exposed to additional heat from nearby heat sources such as engines or electronic components), and may be exacerbated by the cumulative effects of additional loads (such as battery monitoring circuitry often seen in battery management systems).

[0197] A battery may comprise a plurality of battery cells connected in series. In this case, it is necessary to “balance” the battery by maintaining as much voltage / SOC as possible in each cell. Balancing the components that make up the battery cells helps to maximize energy capacity and improve battery life.

[0198] A battery management system (BMS) is used to monitor the condition of the battery pack, including the properties of individual cells, such as temperature and voltage. During charging, the entire battery pack can only be charged until one cell reaches its maximum safe charging voltage, even if other cells still have capacity for further charging. Therefore, the cell with the lowest voltage limits the charging voltage of the entire battery pack. Similarly, the battery pack can only be safely discharged until one cell is fully discharged, even if other cells still have usable charge. Therefore, the cell with the lowest capacity limits the capacity of the entire battery pack. Failure to stop charging / discharging when a cell has reached its limit can permanently damage the cell. Lithium-ion batteries are particularly susceptible to chemical damage from excessive voltage or current.

[0199] Battery balancing redistributes energy from battery cells with higher energy capacity to those with lower energy capacity. Battery balancing can be passive or active. In passive balancing, energy is drawn from the most charged cell and dissipated as heat; in active balancing, energy is drawn from the most charged cell and transferred to the least charged cell. Active battery balancing can be performed using a DC-DC converter.

[0200] A load processing device comprising a component consisting of one or more supercapacitor modules and an energy storage system of a battery can utilize the advantages of a dual power supply by simultaneously drawing a constant low current below a predetermined threshold current from the battery while meeting the acceleration requirements of the load processing device using the supercapacitor. This constant low current below the predetermined threshold current provides optimal conditions for battery cell balancing. The optimal predetermined threshold current will depend on the battery size and specifications and can be determined by the battery manufacturer. For example, the predetermined threshold current can be a current below 3 amps.

[0201] Supercapacitors located at grid positions above access points are charged opportunistically.

[0202] To fulfill customer orders, the load handling unit retrieves the storage container and transports it to a grid position above the access point on the storage grid. The storage container then descends along a chute to the access point, where it can be retrieved to fulfill the order. An operator can remove items from the storage container at the access point and package them as part of the customer order. The load handling unit then raises the storage container through the grid into the container storage space before placing it back into its appropriate position within the storage grid.

[0203] Grid locations above access points on a storage grid are ideal locations for charging components consisting of one or more supercapacitor modules because load handling devices need to frequently travel to these locations to deliver storage containers to the access points. Therefore, a storage system may include one or more supercapacitor charging stations located at grid locations above access points.

[0204] Preferably, the supercapacitor charging station is a high-speed inductive supercapacitor charging station, allowing the supercapacitors to be charged via high-speed inductive charging during raising and lowering operations. This enables the supercapacitors to be fully charged in a short time (in seconds). Because the supercapacitors charge very quickly, charging can be completed within the time spent at the grid position by the load handling device while lowering and raising the storage container. The load handling device frequently accesses the grid position above the access point, so these accesses are sufficient to meet the charging requirements of all supercapacitors. The load handling device does not need to separately access other charging stations to charge components consisting of one or more supercapacitor modules. Therefore, supercapacitor charging can be completed during normal operation of the load handling device without additional time.

[0205] Once the supercapacitor has completed charging at a grid location above the access point on the storage grid during a rise or fall operation, it can be charged with a rechargeable power source. This can be achieved by a controller on the load handling unit instructing a component consisting of one or more supercapacitor modules to charge the rechargeable power source. Alternatively, if the load handling unit is about to proceed to a grid location for a rise or fall operation, the supercapacitor can be pre-charged with a rechargeable power source, thereby partially discharging the supercapacitor and preparing it for charging at a supercapacitor charging station.

[0206] Supercapacitors can be used to charge rechargeable power sources at low currents. As mentioned above, if the rechargeable power source is a battery, subjecting the battery to a low, constant current below a predetermined threshold helps balance the battery cells to ensure a uniform state of charge across the different cells, which can extend battery life. The current can be limited to allow for battery balancing. The controller can instruct the supercapacitor to charge the rechargeable power source at a current below a predetermined threshold.

[0207] If the supercapacitor is charged at a sufficiently high charging rate and frequently enough, the rechargeable power supply may only need to be charged by the supercapacitor. This eliminates the need for separate charging stations on the storage grid to charge the rechargeable power supply. Furthermore, the load processing device no longer needs to travel to the rechargeable power supply station on the storage grid and spend time there while the rechargeable power supply is charging. This effectively eliminates the need for downtime to charge the load processing device, allowing it to operate continuously on the storage grid.

[0208] As described above, the load processing device can be controlled by a control system that monitors the charging level of the rechargeable power source and instructs the load processing device to proceed to a charging station when the charging level drops below a predetermined threshold charging level. In this specific embodiment of the invention, the load processing device can operate continuously on the storage grid without accessing the rechargeable power source charging station, which allows the load processing device to maintain the voltage level of the rechargeable power source above a predetermined threshold voltage for supplying power to the electrical load.

[0209] When the load processing device operates continuously on the storage grid, the recalibration of the estimated battery state, as described above, is particularly important.

[0210] Battery / Supercapacitor Technology

[0211] It should be understood that a component consisting of one or more supercapacitor modules may include, but is not limited to, capacitors, supercapacitors, supercapacitors, lithium capacitors, electrochemical double-layer capacitors, electric double-layer capacitors, pseudocapacitors, hybrid capacitors, or certain combinations of these capacitor technologies.

[0212] It should be understood that rechargeable power sources may include, but are not limited to, lithium-ion batteries, lithium-ion polymer batteries, lithium-air batteries, lithium iron batteries, lithium iron phosphate batteries, lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, sodium-ion batteries, sodium-air batteries, thin-film batteries, solid-state batteries or smart batteries, carbon foam-based lead-acid batteries, or some combination of these technologies.

[0213] Advantages of using a low-pass filter

[0214] Low-pass filters are advantageous for reducing the number of transient current cycles in rechargeable power supplies. High-frequency transients in the current supplied to the electrical load are "eliminated" by the low-pass filter circuit, thus removing high-frequency transient components from the current flowing through the rechargeable power supply. This protects the rechargeable power supply from current surges during current consumption. This is particularly advantageous when the rechargeable power supply is a battery, as reducing transients in the current has been shown to reduce battery aging effects.

[0215] Removing transients means that the rechargeable power supply is no longer affected by any charge-discharge cycles, significantly extending its expected lifespan. Supercapacitors are well-suited for handling transients in current because they have high power density and do not age prematurely due to numerous charge-discharge cycles.

[0216] Using a low-pass filter also improves the efficiency of rechargeable power supplies. Power loss is proportional to the square of the current, so low current results in a significant reduction in power loss.

[0217] In addition to improving efficiency, reducing power consumption is particularly important when load handling units process refrigerated or frozen goods and fulfillment centers need to maintain low temperatures. The heat generated by the rechargeable power supply in the load handling unit means that the fulfillment center's cooling system needs to consume more energy to maintain the required low temperature.

[0218] Highlight the circuit diagram of the low-pass filter.

[0219] Figure 24 This is a circuit diagram showing a rechargeable power supply 100 connected in parallel with an electrical load 104 and a filter circuit 116. The electrical load 104 includes one or more motors that may move the vehicle along the X and Y directions on the track via a group of drive wheels 34 and 36, and / or drive a lifting device or hoisting mechanism to lift the storage container from above.

[0220] For ease of display, Figure 24 The circuit diagram shows the rechargeable power supply 100 as a single battery cell and the electrical load 104 as a single electrical load. It should be understood that the rechargeable power supply of the load handling device is not limited to a battery, and the battery may include a component consisting of one or more battery cells, not just a single battery cell, and the electrical load may include a number of motors and other components, rather than a single electrical load.

[0221] DC-DC converter

[0222] The circuit may additionally include one or more DC-DC converters. For example... Figure 25As shown, the circuit may additionally include a filtered DC-DC converter 118 located between the power load 104 and the filter circuit 116. The filtered DC-DC converter 118 converts the voltage across the rechargeable power supply to a different voltage across the filter circuit. Through a filtered DC-DC converter 118 used in the filter circuit 116, the voltage across the rechargeable power supply can be the same as the load voltage.

[0223] The filtered DC-DC converter 118 between the power load 104 and the filter circuit 116 includes either a boost converter or a buck converter. A buck converter is particularly advantageous if the filter circuit includes one or more supercapacitors connected in parallel with the power load 104, because the voltage across one or more supercapacitors will be lower. Lower voltage means a lower rated supercapacitor or a smaller number of supercapacitors in parallel are required.

[0224] The circuit may additionally include, for example: Figure 26 The source DC-DC converter 108 shown is located between the rechargeable power supply 100 and the filter circuit 116. The function of the source DC-DC converter 108 is to convert the voltage across the rechargeable power supply 100 to a different voltage across the filter circuit 116. It should be understood that, through the two DC-DC converters 108 and 116, the rechargeable power supply 100 and the electrical load 104 can be at the same voltage or different voltages.

[0225] The source-to-DC converter 108 between the rechargeable power supply 100 and the filter circuit 116 may include a boost converter or a buck converter.

[0226] low-pass filter

[0227] A low-pass filter has a cutoff frequency; signals with frequencies below this cutoff frequency are allowed to pass through the filter, while signals with frequencies above this cutoff frequency are attenuated. The filter attenuates high frequencies in the input signal, but signals below the cutoff frequency are hardly attenuated.

[0228] An ideal low-pass filter allows frequencies below the cutoff frequency to pass through the filter without alteration, while completely eliminating all frequencies above the cutoff frequency. Its frequency response is a step function. In practice, electronic low-pass filters are not ideal filters, and the exact frequency response of a filter depends on its design.

[0229] Active and passive filters

[0230] Filtering circuits can be active or passive. Active filters require an external power supply and include an amplification mechanism to increase signal strength. The gain is greater than the overall gain, increasing the available power in the signal relative to the input. Passive filters do not contain an amplification mechanism to enhance the signal and do not require an external power supply. Passive filters cannot have a net power gain and dissipate energy from the signal, resulting in a gain less than the overall gain and an output signal amplitude smaller than its corresponding input signal.

[0231] Passive filtering circuits can be constructed from components such as resistors, inductors, and capacitors. The advantage is that no external power supply is required, as this makes the circuit less complex.

[0232] The advantage of active filters is that they can achieve a specified transfer function over a range of frequencies without using inductors, which are relatively large and expensive components compared to resistors and capacitors. Because they do not use inductors, active filters can be manufactured in a very compact size and do not generate or interact with any magnetic fields that may be present.

[0233] Multi-order filters

[0234] Multi-order filters can be constructed by "stacking" filter circuits together. Higher-order filters exhibit greater signal attenuation as the frequency increases above the cutoff frequency. As the filter's order increases, it approaches the characteristics and operation of an ideal filter.

[0235] Multi-order active filters have the advantage of good isolation between each order, so their characteristics are independent of source and load impedance. In contrast, multi-order passive filters are more difficult to design because each order must take into account the frequency-based load of the previous order.

[0236] Filter circuit examples

[0237] One method for filtering signals is the RC filter, which is a circuit consisting of one or more resistors and one or more capacitors driven by voltage or current sources. The circuit is named "RC" because R and C are the common symbols for resistance and capacitance, respectively. A first-order RC circuit is the simplest type of RC circuit and includes one resistor and one capacitor. RC circuits used for filtering current signals consist of a resistor and a capacitor driven by current sources in parallel. The cutoff frequency is determined by the RC time constant of the circuit. Figure 27a A parallel RC circuit is shown. A first-order RC filter can be constructed using a supercapacitor connected in parallel with the rechargeable power supply 100 and in parallel with the electrical load 104.

[0238] Another method for filtering signals is the RL filter, which is a circuit consisting of one or more resistors and one or more inductors driven by voltage or current sources. The circuit is named "RL" because R and L are common symbols for resistance and inductance, respectively. A first-order RL circuit is the simplest type of RL circuit and includes one resistor and one inductor. RL circuits used for filtering current signals consist of a resistor and an inductor driven by current sources connected in parallel. Figure 27b A parallel RL circuit is shown.

[0239] Another alternative is the RLC filter, which is a circuit consisting of one or more resistors, one or more inductors, and one or more capacitors. A second-order RLC circuit is the simplest type of RLC circuit, consisting of a resistor, an inductor, and a capacitor connected in series or parallel. The circuit is named "RLC" because R, L, and C are the common symbols for resistance, inductance, and capacitance, respectively. Uses of RLC circuits include low-pass filters and other applications. RLC filters are described as second-order filters because the voltage or current in the circuit can be described by a second-order differential equation. Figure 27c A simple RLC circuit is shown.

[0240] Higher-order passive RLC filters, such as the Butterworth filter, can also be used. Figure 27d ).

[0241] The circuits described above are all passive filters. An active low-pass filter circuit can be constructed, for example, by using an operational amplifier. Figure 27e An active filter circuit with an operational amplifier is shown.

[0242] Operational amplifiers are characterized by their gain-bandwidth product (GBWP), which is the product of the amplifier's bandwidth and the gain at the measured bandwidth. The gain-bandwidth product is almost independent of the gain at its measured location, so the gain is roughly inversely proportional to the frequency (to a first approximation). For example, Figure 28 An operational amplifier with a GBWP of 1MHz is shown. This operational amplifier has a gain of 1 (0dB) at 1MHz, a gain of 10 (20dB) at 100kHz, and a gain of 1000 (60dB) at 1kHz. The DC gain of this example is 100000, or 100dB. This inverse response coupled with high DC gain gives the operational amplifier the characteristics of a first-order low-pass filter. The cutoff frequency is obtained by dividing the GBWP by the DC gain. Figure 27cFor the operational amplifier shown, GBWP is 1MHz, DC gain is 100000, and the cutoff frequency is 10Hz. Signals with frequencies of 10Hz and below are allowed to pass through at maximum gain, while signals with higher frequencies have lower gain.

[0243] Increase / decrease transient current during operation

[0244] Figure 19 This demonstrates the transient nature of the current flowing through the load processing devices on the storage grid during both decreasing and increasing operation.

[0245] Figure 29 Another embodiment of the lifting operation of the load handling device is demonstrated. First, the gripper 39 is lowered into the storage grid (deceleration event) to a depth of 21 grid positions. Then, the gripper grasps the storage container 10, weighing 30 kg, and lifts it to the top of the grid and into the container storage space within the load handling device (acceleration event). The gripper then lowers the storage container back to its original position on the storage grid (second deceleration event), releases the container, and then lifts the gripper back to the top of the grid (second acceleration event). From Figure 29 It can be seen that the average current in the first acceleration event when the gripper is loaded with a 30kg storage container is much higher than that in the second acceleration event when the gripper is unloaded. Similarly, the average current in the second deceleration event when the gripper is loaded with a 30kg storage container is much higher than that in the first acceleration event when the gripper is unloaded.

[0246] Table 5 below lists Figure 29 The diagram shows the average current for each of the four acceleration / deceleration events, as well as the peak-to-peak current variation within that event. The variation is significant, with the peak-to-peak variation exceeding 40 amperes in the first acceleration event.

[0247]

[0248] Table 5: Average current and peak-to-peak current variation during lifting and lowering operations.

[0249] Fourier transform of current signal

[0250] To better understand the high-frequency components of current signals, Figures 30a-30d Drawn Figure 29 The Fourier transform of the current signal was plotted. The sampling frequency was 6250 Hz, therefore the range of the Fourier plot is from zero to the Nyquist frequency of 3125 Hz. Figure 30aThe entire Fourier transform was plotted, showing large spikes at low frequencies and a number of smaller spikes in the frequency range up to 1000 Hz. (Overprinted) Figure 30b The same Fourier transform was plotted for the range of 0-1000Hz with amplitude up to 1. It can be seen from the figure that most small impulses have frequencies above 20Hz. Figure 30c The same Fourier transform was plotted for the range of 0-20Hz with amplitude up to 1. It can be seen that the low-frequency peak is below 1Hz, there is a large peak around 9Hz, and a second one appears around 11Hz. Figure 30d Fourier transforms were plotted in the 0-1 Hz range; while the exact shape of the spectrum is difficult to discern at this resolution, a peak can be observed around 0.08 Hz. 0.08 Hz corresponds to a period of approximately 12.5 seconds, which is one cycle of boost and dip operation (from...). Figure 29 It can be seen that the time between the start of the first deceleration event and the start of the second deceleration event is approximately 12.5 seconds, and the time between the start of the first acceleration event and the start of the second acceleration event is also approximately 12.5 seconds.

[0251] By examining the Fourier transform of the current signal, it can be seen that most of the noise in the current lies between 20 Hz and 1000 Hz, with additional impulses at 9 Hz and 11 Hz. A low-pass filter at 20 Hz or 7 Hz will remove most of these transients and generate a smoother signal.

[0252] The above embodiments demonstrate how a predetermined cutoff frequency can be determined through the Fourier transform of a signal. When the predetermined cutoff frequency is known, the filter circuit can be designed to function as a low-pass filter, allowing frequencies below the predetermined cutoff frequency to pass while reducing frequencies above the predetermined cutoff frequency.

[0253] For passive low-pass filter circuits, component specifications can be selected to ensure the circuit frequency equals a predetermined cutoff frequency. For example, in an RC filter circuit, resistor and capacitor values ​​can be selected to make the circuit frequency the desired cutoff frequency. In an RL filter circuit, resistor and inductor values ​​can be selected to make the circuit frequency the predetermined cutoff frequency. In an RLC filter circuit, resistor, inductor, and capacitor values ​​can be selected to make the circuit frequency the predetermined cutoff frequency.

[0254] For active low-pass filter circuits using operational amplifiers, the characteristics of the operational amplifiers can be selected so that the circuit's cutoff frequency is the same as the predetermined cutoff frequency. (As mentioned above...) Figure 28 The cutoff frequency of the operational amplifier, as described above, can be calculated by dividing its GBWP by its DC gain.

[0255] Low-pass filter RC circuit

[0256] The principles of designing a low-pass filter circuit with a predetermined cutoff frequency will be demonstrated using a first-order RC filter. It should be understood that this specific circuit is one of many possible implementations of the filter design and is not intended to be limiting.

[0257] Figure 27a This diagram illustrates a simple first-order RC filter circuit with resistors and capacitors connected in parallel. The filter's time constant is calculated by multiplying the resistors and capacitors, therefore the cutoff frequency f is obtained using Equation 1:

[0258] Equation 1

[0259] Where R is the resistance of the circuit and C is the capacitance of the circuit.

[0260] The reactance X is derived from Equation 2. At higher frequencies, the reactance decreases, and the capacitor effectively functions as a short-circuit circuit.

[0261] Equation 2.

[0262] The low-frequency components of a current signal are attenuated by the capacitor's reactance; the current does not flow freely through the capacitor but accumulates at its plates. Pure direct current (the zero-frequency component of the current signal) will not pass through the capacitor at all, so it must be diverted through a resistor. Low-frequency components are not completely blocked by the capacitor, but their amplitude will be reduced and at least part of the current will be directed through the resistor.

[0263] The high-frequency component of the current signal passes through the capacitor very smoothly because the capacitor has almost no time to accumulate charge before the high-frequency component of the current changes direction. The current preferentially flows through the capacitor rather than through the resistor, effectively shortening the circuit.

[0264] In practice, capacitors operate between these two extremes because the current signal comprises components across a range of frequencies.

[0265] Regarding the above and Figure 29 The current signal shown is examined ( Figures 30a-30d The Fourier transform of the current signal (shown) indicates that a predetermined cutoff frequency of around 20 Hz or (preferably) around 7 Hz is suitable. Equation 1 can be used to select appropriate R and C values ​​to create a filter circuit with a circuit frequency of 20 Hz or 7 Hz.

[0266] Equation 1 can be reset to calculate the required capacitance (Equation 3):

[0267] Equation 3.

[0268] Using a resistor with a resistance of 3.5 mΩ, Equation 3 shows that the required capacitance for the 20Hz circuit is 2.3F, and the required capacitance for the 7Hz circuit is 6.6F.

[0269] Simulation demonstrates the effectiveness of low-pass filtering.

[0270] Figure 31 This is a Simulink model of a simple RC filter circuit with a resistor and capacitor connected in parallel. The 48V voltage source represents a rechargeable power source, and the capacitor represents a power load. The resistor has a resistance of 3.5 mΩ. Figure 29 The current signal is applied through the resistor, and the current signal in the rechargeable power supply is plotted.

[0271] Figures 32a-32c The current signals passing through the resistor and the rechargeable power supply are plotted. As calculated above, a filter circuit with a circuit frequency of 20Hz should filter out most of the transients from the current signal. Figure 32a It is the original current signal, and Figure 29 The same as in [the previous sentence]. Figure 32b The filtered signal is obtained by using an RC filter circuit with a circuit frequency of 20Hz, a resistor resistance of 3.5 mΩ, and a capacitor capacitance of 2.3 Farad at the rechargeable power supply. It can be seen that the transients in the current passing through the rechargeable power supply are significantly reduced compared to the input current. The input current experiences a 47-amp impulse at the start of the first acceleration event around 6.5 seconds; this impulse is significantly reduced to 33 amps at the rechargeable power supply. This demonstrates that using a capacitor in the filter circuit reduces transients and impulses in the current, thus reducing the aging effect on the rechargeable power supply.

[0272] As calculated above, a filter circuit with a frequency of 7Hz should filter out transients from the current signal in the same way as a 20Hz circuit, and also filter out the peaks observed at 9Hz and 11Hz. Figure 32c The filtered signal is obtained by using an RC filter circuit with a circuit frequency of 7Hz, a resistor resistance of 3.5 mΩ, and a capacitor capacitance of 6.6 Farad at the rechargeable power supply. It can be seen that the transient current in the current passing through the rechargeable power supply is significantly reduced compared to the input current; the 7Hz filter circuit reduces the frequency even more than a 20Hz filter circuit. The input current experiences a 47-amp surge at the start of the first acceleration event around 6.5 seconds; this surge is reduced to 26 amps at the rechargeable power supply. Compared to the average current of 24 amps during the first acceleration event, this surge is relatively small.

[0273] Table 6 below lists the average current for each of the four acceleration / deceleration events, the peak-to-peak current variation within that event, and the peak-to-peak current variation after filtering at 20Hz and 7Hz. It can be seen that the peak-to-peak variation is significantly reduced due to filtering.

[0274]

[0275] Table 6: Average current and peak-to-peak current variations during boost and deboost operations after filtering at 20Hz and 7Hz.

[0276] Figure 33a The load current was compared with the current passing through a rechargeable power supply with a 20Hz filter circuit. Figure 33b The load current and the current passing through a rechargeable power supply with a 7Hz filter circuit were compared. These figures readily demonstrate how transients in the current signal are significantly reduced.

[0277] Nonlinearity of lithium-ion batteries

[0278] Figure 34 A typical discharge curve for a lithium-ion battery is shown, plotting the cell voltage relative to the discharge capacity. Discharge capacity is defined as 100% minus the state of charge: 100% state of charge corresponds to 0% discharge, and 0% state of charge corresponds to 100% discharge. It can be seen that the discharge curve is highly non-linear. This means that in practice, a lithium-ion cell does not operate across the entire voltage range. While the voltage range of a single lithium-ion cell can reach 4.2V, the highly non-linear shape of the curve in practice means that the cell operates between 3 and 4 volts most of the time. This graph only shows a symbolic voltage curve; in practice, the shape of the curve depends on many factors, such as temperature and discharge rate. Other battery chemistry formulations have different maximum voltages and different discharge curves, but are also non-linear. This can be a problem for rechargeable power supplies that handle battery loads, as these load handling devices cannot utilize the full battery range.

[0279] To power one or more load motors, several lithium-ion battery cells can be connected in series. For example, 12 lithium-ion battery cells connected in series provide a voltage range of up to 12 * 4.2 = 50.4V, sufficient to power one or more load motors at a nominal voltage of 48V. Lithium-ion (battery) cells operate mostly between 36V (12 x 3V) and 48V (12 x 4V). In practice, lithium-ion batteries utilize only a small fraction of their full voltage range (and therefore only a small fraction of their total energy storage).

[0280] However, in practice, once the voltage of the lithium-ion battery pack drops below the threshold voltage used to power the electrical load, the load motor will not have enough power to provide the necessary acceleration for the load handling device. This can happen before the lithium-ion (battery) cells are fully discharged, meaning that only a portion of the effective range of the lithium-ion (battery) cells is being used to power the load. Once the threshold voltage is reached, the battery will not be able to provide enough power, and the load handling device must be recharged. For a load handling device with a 48V lithium-ion battery pack and a 48V electrical load, this threshold voltage is approximately 42.6V.

[0281] In some implementations, load processing devices may need to achieve predetermined acceleration to perform their functions. To achieve the item throughput of the storage system required to fulfill orders and meet demand, load processing devices must operate on the grid at the maximum possible acceleration. The greater the acceleration of a load processing device operating on the grid, the faster it can reach the desired grid cell when retrieving or storing storage containers from a given stack. Conversely, the less acceleration a load processing device operates on the grid, the longer it takes to reach the desired grid cell and therefore more time to retrieve storage containers from the given stack. Consequently, to maintain the item throughput of the storage system and thus meet lower acceleration requirements, a larger number of load processing devices will be needed to operate on the grid.

[0282] The storage system includes a control system that manages the movement of workloads across the grid. This control system tracks the position of each workload, instructs it to move to a new location, and avoids collisions. If a workload cannot achieve the required acceleration, it may fail to make the necessary movement within the expected timeframe. Other workloads may need to slow down or detour to avoid collisions. Besides significantly complicating control, this can slow down or disrupt the paths of other workloads on the grid, not just those that are under-accelerated.

[0283] Therefore, in some embodiments, it may be advantageous to define a predetermined acceleration for the load handling device to achieve its function. This could be a linear acceleration of the load handling device moving along tracks on a grid frame structure, or an acceleration of the gripper lifting the container from the storage system into the container storage space of the load handling device, or both. The predetermined acceleration defines the torque requirement of the lifting drive assembly and / or drive mechanism, and thus the torque requirement of the engine. The torque requirement defines a threshold voltage. This voltage will be referred to as the predetermined threshold voltage because its value is defined by the predetermined acceleration. This is commonly referred to as the operating voltage of the electrical load. When the engine voltage drops below this predetermined threshold voltage, the load handling device will not be able to achieve the predetermined acceleration. In an exemplary embodiment, for a load handling device with a 48V lithium-ion battery pack and a 48V electrical load, the predetermined threshold voltage is approximately 42.6V.

[0284] The usable portion of the battery voltage range is thus further reduced. For example, a 5kWh lithium-ion battery might only use the first ~1.5kWh (the first third) of its energy capacity. This is problematic because the battery is very expensive and heavy, but only a portion of its capacity is usable, so the battery must be charged more frequently than actually needed. Charging requires downtime as well as the time and energy spent by the load handling unit traveling to and from charging stations on the storage grid.

[0285] The problem to be solved is how to extend the operating time of the load handling device before it needs to be charged by a rechargeable power source.

[0286] One way to increase the time between charging cycles is to increase the voltage of the rechargeable power supply. However, this is a suboptimal option because higher voltage requires more safety measures to protect human operators. Higher voltage also requires components with higher power ratings, resulting in higher costs. Furthermore, increasing the voltage does not solve the problem of the rechargeable power supply operating only within a portion of its effective range.

[0287] Another approach is to use a second power source as a "booster" to utilize a higher proportion of the rechargeable power source's operating voltage, so that the energy storage system can provide sufficient power when the voltage of the rechargeable power source has dropped below a predetermined threshold voltage used to power the electrical load.

[0288] Supercapacitors can be connected in parallel with rechargeable power sources, allowing both to supply power to the load at the same voltage. However, this is not ideal, as it only utilizes a portion of the supercapacitor's effective voltage range. The cost per unit of energy stored in a supercapacitor is higher than that of a rechargeable power source, and several supercapacitor modules connected in series may be required to achieve the desired voltage.

[0289] Figure 35The typical discharge curves of batteries and supercapacitors were compared. The discharge curve of a supercapacitor is approximately linear, with the voltage decreasing linearly with the amount of discharge (defined as 100% - state of charge). The battery discharge curve is much flatter, therefore, for the same voltage change, the battery will experience a greater change in state of charge. When a battery and a supercapacitor are connected in parallel, they will experience the same voltage drop. The difference in discharge curve shape means that when a parallel battery and supercapacitor experience the same voltage drop, the battery's state of charge will drop more than the supercapacitor's because the battery's discharge curve is much flatter. The supercapacitor will therefore experience a smaller change in state of charge and only utilize a small portion of its SOC range. Therefore, a disadvantage of circuits including parallel connections of supercapacitors and batteries, both supplying electrical loads, is that only a portion of the supercapacitor's full SOC range can be utilized.

[0290] Supercapacitor connected in series with a rechargeable power supply as a boost converter

[0291] Another way to use supercapacitors as power boosters is to connect them in series with a rechargeable power source. Because the discharge curve of a supercapacitor is linear, its entire voltage range can be utilized.

[0292] Because supercapacitors have low energy density and are more expensive per unit of energy storage than other rechargeable power sources, supercapacitors with lower nominal voltages can be used. Connecting a component consisting of one or more supercapacitors in series with a rechargeable power source means that the nominal voltage of the supercapacitors can be lower than the nominal voltage of the rechargeable power source – eliminating the need to connect multiple supercapacitor units in series to match the voltage of the rechargeable power source – thus allowing the use of fewer supercapacitor units.

[0293] Connecting a supercapacitor in series with a rechargeable power source means that if the combined voltage across the supercapacitor and the rechargeable power source is greater than or equal to a predetermined threshold voltage for supplying power to the load, the load handling device can continue to operate even if the voltage across the rechargeable power source has dropped below the predetermined threshold voltage. In practice, this means that the load handling device can operate for a longer period between charging sessions at a charging station.

[0294] In the embodiments given above, for a load processing device with a 48V lithium-ion battery pack and a 48V power load, the predetermined threshold voltage is approximately 42.6V. If only the battery is present, the load processing device would need to be recharged once the battery voltage drops to 42.6V. However, with a 5V supercapacitor connected in series with the battery, the load processing device can continue operating until the battery voltage drops to 37.6V, even after the combined voltage across the battery and supercapacitor (5V + 37.6V) has dropped to the predetermined threshold voltage of 42.6V.

[0295] Supercapacitors with voltages of 2.7 or 5.4V are readily available commercially. Other voltages are also available.

[0296] For short-term peak power demand only

[0297] As mentioned above, the energy storage system of the load handling device must be able to provide sufficient power to the drive mechanism and / or boost drive components to complete acceleration events. However, deceleration events do not have a constant power requirement.

[0298] Peak demand for electricity only occurs for a short period of time. Figure 36 The power demand for the engine powering the wheels of the load processing unit as it moves on top of the storage grid is plotted. It can be seen that the peak power demand occurs at approximately 1.1 seconds and lasts for less than 1 second. Therefore, the energy storage system only needs to provide maximum power for a short period. Supercapacitors are perfectly suited to provide this power surge due to their high power density and low energy density. Since the demand lasts only a short time, a high energy storage capacity is not required. Supercapacitors can help meet the power demand without significantly increasing the mass or cost of the energy storage system.

[0299] See also deceleration events Figure 36 This occurs between approximately 1.3 and 2 seconds. During this period, the power demand is negative, meaning the engine is acting as a generator and recovering energy from the deceleration of the load handling unit.

[0300] The energy storage system of the load handling unit must be able to power the gripper to be lowered and raised by the lifting drive assembly to retrieve or stack storage containers. As mentioned above, Figure 29 This demonstrates an example of the lifting operation of a load handling unit. From Figure 29 It can also be seen that the peak demand of the power load only occurred for a short period of time. The peak power demand of the first acceleration event occurred at approximately 6.5 seconds and lasted for less than 1 second. Therefore, the energy storage system only needs to provide maximum power for a short period. Supercapacitors are perfectly suited to provide this power surge because of their high power density and low energy density. Since the demand only lasts for a short time, a high energy storage capacity is not required. Supercapacitors can help meet the power demand without adding significant additional mass or cost to the energy storage system.

[0301] Circuit diagram of supercapacitor connected in series with rechargeable power supply

[0302] Figure 37A simplified circuit diagram is shown, illustrating the series connection of supercapacitor 102 and rechargeable power supply 100. Together, the supercapacitor and rechargeable power supply power the electrical load 104. During normal operation, both the rechargeable power supply 100 and the supercapacitor 102 supply power to the electrical load 104.

[0303] Figure 37 A single battery cell 100, a single supercapacitor 102, and a single electrical load 104 are shown for illustrative purposes only. The rechargeable power supply 100 is not limited to a battery and may include a plurality of battery cells connected in series and / or in parallel. Battery cells may be connected in series to increase voltage (e.g., a battery with a rated voltage of 48V may include 12 lithium-ion battery cells connected in series, each with a maximum voltage of 4.2V), and / or connected in parallel to increase energy storage capacity. The supercapacitor 102 may include a plurality of supercapacitors connected in series or in parallel, with series connection increasing voltage and parallel connection increasing energy storage capacity. The electrical load 104 may include a plurality of motors or other components. For example, the electrical load may include one or more motors as part of a lifting drive assembly and one or more motors as part of a drive mechanism to drive the wheels of the load handling device.

[0304] Figure 38 A circuit diagram is shown showing a rechargeable power supply 100 including a plurality of battery cells connected in series, a supercapacitor 102 including a plurality of supercapacitor modules connected in series and parallel, and an electrical load 104 including a plurality of motors connected in parallel.

[0305] Ground 105 is common; all grounding components can be connected to the chassis of the load handling unit.

[0306] Controlling supercapacitor charging

[0307] The controller 120 can be used to manage the charging and discharging of the supercapacitor 102. The controller can be configured to instruct the rechargeable power supply 100 to charge the component consisting of one or more supercapacitor modules when the voltage across the component is lower than a predetermined threshold supercapacitor recharge voltage.

[0308] The predetermined threshold supercapacitor recharge voltage can be limited to be sufficiently low than the supercapacitor's maximum rated voltage, so that there is enough unused energy storage capacity to receive energy recovered from deceleration events.

[0309] The DC-DC converter 122 can be used to convert the voltage between a rechargeable power supply 100 and a component consisting of one or more supercapacitor modules.

[0310] When energy is recovered from the drive mechanism and / or lift drive assembly of the load handling device during a deceleration event, if the voltage across the assembly consisting of one or more supercapacitor modules is lower than a predetermined threshold supercapacitor recharge voltage, the controller directs the recovered energy to the assembly consisting of one or more supercapacitor modules.

[0311] A DC-DC converter can be used to convert the voltage between a load voltage and the voltage between a component consisting of one or more supercapacitor modules. It can be the same as DC-DC converter 122 used to convert the voltage between a rechargeable power supply and a component consisting of one or more supercapacitor modules.

[0312] An assembly consisting of one or more supercapacitor modules may be selected such that its rated power is sufficient to accommodate the power recovered from the drive mechanism and / or lift drive assembly during a deceleration event, and its energy storage capacity is sufficient to accommodate and store the energy recovered from the drive mechanism and / or lift drive assembly during one or more deceleration events. This ensures that all available recovered energy is available for acquisition and storage.

[0313] Figure 39 and 40 The circuit's control operation is demonstrated. Controller 120 reads the voltage Vb across the rechargeable power supply and the combined voltage Vc across the rechargeable power supply and the supercapacitor. The voltage difference Vc – Vb between these two voltages is the voltage across the supercapacitor. If the voltage across the supercapacitor falls below a predetermined threshold supercapacitor recharge voltage, the controller charges the supercapacitor. The input current Iin to the controller can be supplied by the rechargeable power supply or by braking current recovered from the drive mechanism and / or boost drive components during deceleration events. DC-DC converter 122 can be used to convert the voltage of this input current to supply the supercapacitor with an appropriate voltage.

[0314] Figure 39 This demonstrates the operation of the circuit when the rechargeable power supply 100 is used to charge the supercapacitor 102. Figure 39 The arrows above indicate the direction of current flow. The rechargeable power supply 100 supplies power to the electrical load 104 and the supercapacitor 102 via the controller 120 and the DC-DC converter 122.

[0315] Figure 40 The circuit operation is demonstrated when energy recovered from electrical load 104 is used to charge supercapacitor 102. Figure 40 The arrows above indicate the direction of current flow. The energy recovered from the electrical load 104 is supplied to the supercapacitor 102 via the controller 120 and the DC-DC converter 122.

[0316] Figure 41 A more detailed description of a possible specific implementation of the controller 120 and the DC-DC converter 122 is provided. If the voltage Vc – Vb across the supercapacitor falls below a predetermined threshold supercapacitor recharge voltage, the controller 120 sends a signal, which can be a square wave, to the base of the transistor 124. When the transistor 124 is activated, it allows the input current Iin to flow to ground 105 via the first coil of the transformer 126. The current is then introduced into the second coil of the transformer 126. This current passes through the rectifier 128 and is then used to charge the supercapacitor 102. The controller 120 measures the voltage feedback Vfb and the current feedback Ifb to monitor the output voltage and current from the DC-DC converter 122.

[0317] Switch 130 can be used to protect supercapacitor 102 from overcharging. Controller 120 can detect when the supercapacitor voltage is too high, such as exceeding the maximum supercapacitor voltage, and then operate the switch to disconnect the supercapacitor from the power supply. Switch 130 is shown here located between controller 120 and the base of transistor 124, but it should be understood that the switch can be located anywhere in the circuit that disconnects supercapacitor 102 from the power supply.

[0318] Supercapacitor Protection Circuit

[0319] During normal operation, supercapacitor 102 discharges and supplies power to electrical load 104. When the supercapacitor is fully discharged, it can no longer supply power. Supercapacitor protection circuit 132 can be used to ensure that the supercapacitor will not reverse charge once it is fully discharged. Reverse charging can damage the supercapacitor.

[0320] Figure 42 This is a partial circuit diagram showing the supercapacitor protection circuit 132 bypassing the supercapacitor 102. During normal operation, the supercapacitor is charged or partially charged and discharges as current flows through it. When the supercapacitor is discharging, the supercapacitor protection circuit 132 allows current to bypass the supercapacitor instead of flowing through it.

[0321] The supercapacitor protection circuit 132, which prevents reverse charging of the supercapacitor, may include a transistor. The transistor may be controlled by a supercapacitor protection circuit controller 134. When the voltage across the supercapacitor 102 drops below zero volts, the supercapacitor protection circuit controller 134 sends a signal to the base of the transistor 132 to turn it on, thus allowing current to flow through the transistor 132 instead of through the supercapacitor 102. The supercapacitor protection circuit controller 134 may be a standalone device or integrated into the same controller 120 that controls the charging of the supercapacitor.

[0322] The rules for controlling supercapacitors are summarized as follows:

[0323] 1. If the voltage across the supercapacitor 102 is lower than the predetermined threshold supercapacitor recharge voltage, then the controller 120 instructs the rechargeable power supply 100 to charge the supercapacitor 102 through the DC-DC converter 122.

[0324] 2. If the voltage across the supercapacitor 102 is lower than the predetermined threshold supercapacitor recharge voltage, then the controller 120 directs any recovered energy from the drive mechanism and / or boost drive components to the supercapacitor 102 via the DC-DC converter 122.

[0325] 3. If the voltage across the supercapacitor 102 is lower than 0, the supercapacitor protection circuit controller 134 will activate the supercapacitor protection circuit 132 to prevent the supercapacitor 102 from being reverse-charged.

[0326] 4. If the supercapacitor voltage is higher than the maximum supercapacitor voltage, then the controller 120 turns on the switch 130 to disconnect the power supply from the supercapacitor and protect the supercapacitor 102 from overcharging.

Claims

1. A storage system comprising a grid framework (14) of aisles arranged in a grid pattern above a stack (12) of containers (10) supported by the grid framework (14) and a plurality of load handling devices (30) for lifting and moving one or more containers (10) stacked in the storage system, the load handling devices (30) comprising: i) a carrier body (32) housing a drive mechanism operatively arranged for moving the load handling device (30) on the grid framework (14); ii) a lifting device comprising a lifting drive assembly and a gripper device (39) configured in use to releasably grasp a container (10) and lift the container (10) from the stack (12) into a container receiving space; wherein the lifting drive assembly and / or the drive mechanism comprises at least one motor constituting a power load (104); iii) a rechargeable power source (100); iv) an assembly of one or more supercapacitor modules (102); characterized in that the power load (104) is connected across the assembly of one or more supercapacitor modules (102) and the rechargeable power source (100) is connected in parallel to the assembly of one or more supercapacitor modules (102) such that the rechargeable power source (100) is configured to power the assembly of one or more supercapacitor modules (102), wherein the storage system further comprises one or more supercapacitor charging stations located at grid locations above access points, wherein the assembly of one or more supercapacitor modules (102) on the load handling device (30) is charged by one of the one or more supercapacitor charging stations during lifting or lowering operations.

2. The storage system of claim 1, wherein, The load handling device (30) further comprises a load DC-DC converter (110) located between the assembly of one or more supercapacitor modules (102) and the power load (104).

3. The storage system according to claim 2, wherein the load DC-DC converter located between the assembly of one or more supercapacitor modules (102) and the power load (104) is a step-up converter.

4. The storage system of claim 1, wherein, The load handling device (30) further comprises a source DC-DC converter (108) located between the rechargeable power source (100) and the assembly of one or more supercapacitor modules (102).

5. The storage system according to claim 4, wherein the source DC-DC converter located between the rechargeable power source (100) and the assembly of one or more supercapacitor modules (102) is a step-down converter.

6. The storage system of claim 1, wherein the controller (114) is configured to vary the power supplied from the rechargeable power source (100) to the assembly of one or more supercapacitor modules (102).

7. The storage system of claim 6, wherein the controller (114) is configured to instruct the rechargeable power source (100) to supply power to the assembly of one or more supercapacitor modules (102) when a voltage of the assembly of one or more supercapacitor modules (102) is below a predetermined supercapacitor target voltage threshold.

8. The storage system of claim 7, wherein the predetermined supercapacitor target voltage threshold is below a maximum rated voltage of the assembly of one or more supercapacitor modules (102).

9. The storage system of any one of claims 6-8, wherein the controller (114) is configured to instruct the rechargeable power source (100) to supply power to the assembly of one or more supercapacitor modules (102) at a predetermined threshold current for effecting battery balancing.

10. The storage system of any one of claims 6-8, wherein the controller (114) is configured to periodically disconnect the rechargeable power source (100) from the assembly of one or more supercapacitor modules (102) in use, such that the rechargeable power source experiences a low current drain period in which it does not supply power to the assembly of one or more supercapacitor modules (102).

11. The storage system of claim 1, wherein, The load handling device (30) further comprises an energy recovery circuit (112) to divert energy regenerated from the drive mechanism and / or the lift assembly to the assembly of one or more supercapacitor modules (102), wherein the energy recovery circuit (112) comprises a diode or a transistor.

12. The storage system of claim 1, wherein the assembly of one or more supercapacitor modules (102) has a lower internal resistance than the rechargeable power source (100).

13. The storage system of claim 1, wherein the electrical load (104) comprises a first portion and a second portion, wherein the first portion of the electrical load (104) comprises a motive electrical load, and the second portion of the electrical load (104) comprises a non-motive electrical load (106).

14. The storage system of claim 13, wherein the rechargeable power source (100) is configured to supply power to the non-motive electrical load (106).

15. The storage system of claim 1, wherein the assembly of one or more supercapacitor modules (102) is configured as a primary power source for the load handling device (30), and the rechargeable power source (100) is configured as a secondary power source for supplying power to the primary power source.

16. The storage system of claim 15, wherein the controller (114) is configured to instruct the rechargeable power source (100) to supply power directly to the electrical load (104) when the voltage across the assembly of one or more supercapacitor modules (102) is below a predetermined supercapacitor voltage threshold.

17. The storage system of claim 1, wherein the assembly of one or more supercapacitor modules (102) is distributed around the exterior of a container-receiving recess within the vehicle body (32) of the load handling device (30), between an outer wall (42) and an inner wall (44) of the load handling device (30).

18. The storage system of claim 1, wherein the one or more supercapacitor charging stations are inductive supercapacitor charging stations.

19. The storage system of claim 6, wherein the controller (114) on the load handling device (30) is configured to instruct the assembly of one or more supercapacitor modules (102) to charge the rechargeable power source (100).

20. The storage system of claim 6, wherein the controller (114) is configured to instruct the one or more supercapacitor modules (102) to supply power to the rechargeable power source (100) at a predetermined threshold current for battery balancing.

21. A fulfillment center comprising the storage system of claim 1.

22. The fulfillment center of claim 21, wherein the temperature within the fulfillment center is any one of the following temperatures: an ambient temperature of 4°C or greater; a refrigerated temperature of approximately 0° to approximately 4°C; a frozen temperature of approximately -25°C to approximately 0°C.

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