Patent Application
20220271566
According to a first aspect, there is provided a method of transferring power through a metamaterial structure comprising configuring a metamaterial structure comprising a plurality of electrical resonators that support magnetoinductive waves to wirelessly transmit power to a receiver located adjacent to one or more target resonators of the metamaterial structure, the method comprising:
According to a second aspect, there is provided an apparatus comprising:
The optional features described below are equally applicable to the first and second aspect. The system controller and apparatus may be configured to perform optional features of the method. The method may utilise a specific apparatus with any of the features recited below.
Adjusting parameters may comprise adjusting parameters of the metamaterial structure to create constructive interference of one two or three dimensional magnetoinductive waves at the target resonator.
The plurality of resonators may support dispersive magnetoinductive waves.
There may be a plurality of target resonators, and improving power transfer may comprise increasing the uniformity of current intensity in the target resonators. Reference to a target resonator does not exclude the possibility of there being more than one target resonator, for instance corresponding with more than one target device in different locations. Statements referring to a target resonator may also apply to target resonators (mutatis mutandis).
The metamaterial structure may comprise an array or lattice of resonators.
The electrical resonators may be provided on a plurality of substrates or tiles. Each electrical resonator may be provided on a separate tile. Each tile may be a printed circuit board. In other embodiments, more than one of the resonators may be disposed on a single tile (e.g. some tiles may include two or more resonators).
The electrical resonators may be placed next to each other in an array or lattice (the lattice or array may be two dimensional or three dimensional). Adjusting at least one of the electrical resonators may comprise removing one of the resonators from the array or lattice, leaving a defect. The method may comprise forming the metamaterial structure by placing substrates comprising the resonators side-by-side. Placing at least some of the substrates side-by-side may comprise placing some (or all) of the substrates with at least one edge in contact with a neighbouring substrate.
A set of electrical resonators can be configured as the metamaterial structure capable of supporting magnetoinductive waves by placing the resonators in a two-dimensional or three-dimensional array or lattice, where adjacent resonators have a coupling coefficient (defined as the ratio of mutual inductance and the geometric mean of the self-inductance of the adjacent resonators) of at least 0.01 and a Q factor of at least 20. More preferably the coupling coefficient is at least 0.05 and the Q factor is at least 100.
Each of the plurality of substrates may have the same shape (e.g. rectangular or square). This facilitates straightforward tiling/tessellation of the elements into an array. Each substrate (and/or each electrical resonator) may have a polygonal shape, such as triangular, square, rectangular, pentagonal, hexagonal etc. Polygons with fewer sides may have increased inductive coupling with each neighbouring resonator. A mixture of different shapes may be used in the system.
Powering at least one of the electrical resonators may comprise injecting current directly into the powered at least one electrical resonator via a direct electrical connection, and/or exciting a current in the powered at least one electrical resonator inductively (e.g. by resonant and/or inductive power transfer).
The metamaterial structure may be configured to support MIWs with a frequency that is near to a nominal resonant frequency (e.g. within 5%, or 10%) of each of the electrical resonators (excluding any electrical resonators that are configured as defects).
Parameters of the metamaterial includes geometrical and/or electrical/electromagnetic parameters. Adjusting parameters of the metamaterial structure may comprise one or more of: adjusting one or more of the resonators in the metamaterial structure; creating one or more lattice defect in the metamaterial structure from which MIWs are scattered and/or reflected.
The defects may be temporally periodic (e.g. in addition to being spatially periodic). The defects may be configured to produce a checkerboard pattern of alternating high and low currents in a region of the electrical resonators of the structure. The method may comprise switching from a first configuration of defects with a first checkerboard pattern of high current resonators, and a second configuration of defects with a second pattern that is substantially an inverted version of the first pattern (with, for a majority of the resonators that are not configured as defects, low current resonators where there were previously high current resonators, and high current resonators where there were previously low current resonators).
The defects in the metamaterial structure may comprise electrical resonators at that are: not present, detuned, or switched off. A switched off electrical resonator may be one with electrical properties that are significantly different to the electrical resonators that do not comprise defects in the material, for instance having an electrical impedance that is at least twice as high at the system frequency, a Q that is at least twice as low, and/or a resonant frequency that differs from the system frequency by at least 10%.
The system frequency may be a nominal resonant frequency of each electrical resonator (e.g. in the on state).
The method may comprise placing a defect on a symmetry axis/plane of the Brillouin scattering zone of the metamaterial structure to reflect and/or scatter a beam formed along the symmetry axis/plane.
The metamaterial structure may approximate a square 2D array, and the method may comprise placing a defect on a diagonal from a powered electrical resonator.
The method may comprise placing a pattern of defects along at least one edge of the array to create a specific standing wave pattern over the structure. The standing wave pattern may approximate a checkerboard pattern of alternating high and low current intensity over a region of the structure.
The pattern of defects along at least one edge comprise may comprise defects in each corner of the structure. More generally, defects may be placed perpendicular to at least one symmetry axis (or on each axis) of the Brillouin scattering zone of the lattice—for a square lattice, this corresponds to a triangular blocking element in each corner, since the Brillouin scattering symmetry axes are diagonal. For a triangular lattice, six blocking regions may be advantageous.
The defects in each corner may together form triangular shapes in each corner.
Creating one or more defect in the structure may comprise creating a plurality of lambda-periodic defects in that have a spatial period in at least one direction corresponding with a wavelength of the MIWs from the at least one powered electrical resonator. Note that the wavelength of the MIW is not the same as the wavelength of an electromagnetic wave of the same frequency propagating in space. The wavelength is defined by the propagation of the excitation current through the resonators of the metamaterial.
The lambda-periodic defects may comprise, or consist entirely of, features at edge regions of the structure.
The lambda-periodic defects may comprise a lambda-grid of defects across a region, or all of, the array. For a lattice comprising a square array, the lambda grid may comprise a defect at every fifth resonator element.
Creating one or more defect in the array may comprise creating a defect at every second electrical resonator along the edges of the array.
Adjusting at least one of the electrical resonators may comprise adjusting an effective impedance of the at least one electrical resonator.
At least one of the electrical resonators may be a controllable resonator that comprises part of a controllable element, the controllable element further comprising a control device.
Creating one or more defects in the metamaterial structure may comprise using a control signal to switch the controllable resonator from an on state to an off state.
The controllable resonator may have a first resonant frequency in the on state and a first impedance at the resonant frequency in the on state, and in the off state a second impedance at the first resonant frequency that is at least 10 times less than the first impedance. In the off state the controllable resonator may not have a resonant frequency that is within 5% of the first resonant frequency. In the off state the controllable resonator may not have a resonant frequency that is within 50% of the first resonant frequency. In the off state the controllable resonator may have a resonant frequency that is at least 1.5 times the first resonant frequency, preferably at least 2 times the first resonant frequency. It has been found experimentally that this provides effective control. For example, for a nominal (first) frequency of 6.78 MHz, it was found that the effectiveness of control is reduced if the second resonant frequency is less that 15 MHz.
The controllable resonator may comprise a primary resonator, and the control device may further comprise an active control component that is configured to adjust the effective impedance of the primary resonator in response to a control signal.
The control device may comprise a secondary resonator, inductively coupled to the primary resonator, the active control component configured to vary the electrical properties of the secondary resonator in response to the control signal.
The coupling between the controllable resonator and secondary resonator may mean that the coupled system will have two modes: a first mode in which the currents in the primary and secondary resonator are in phase, and a second mode in which the currents in the primary and secondary resonator are out of phase.
The secondary resonator may be operable in the off state to cause an anti-resonance in the system of the primary resonator and secondary resonator at the resonant frequency of the primary resonator.
Adjusting parameters may comprise communicating the control signal.
The system controller may be configured to provide the control signal wirelessly.
The control signal may be communicated by an in-band communication channel that propagates as a modulated MIW through the structure.
The system controller may be configured to provide the wireless control signal by an in-band wireless communication signal that propagates as a modulated MIW through the structure. The system controller may be configured to provide the wireless communication signal out-of-band, for example via Bluetooth or Zigbee. The system controller may comprise a modem for transmitting and receiving wireless signals (in-band or out-of-band). At least one (or each) of the electrical resonators may be provided with a receiver for receiving control signals from the system controller and/or a transmitter (or a modem with Tx/Rx functionality) for transmitting information about the status of the resonator (e.g. current flow) to the system controller.
The method may comprise locating the target resonator by determining which electrical resonator has the best coupling to a target device placed in proximity to the structure.
At least one or each of the electrical resonators may be provided with a current sensor for detecting current flow in the electrical resonator. The current sensor may comprise a Hall sensor.
Locating the target resonator may comprise:
For example, half of the electrical resonators could be placed in an ‘off’ state, and half in an ‘on’ state. If the target device is receiving power from the structure in this configuration, the target resonator is in the set of devices that were placed in the ‘on’ state. A binary search for the target device can be conducted using this approach.
Alternatively (or additionally), electrical characteristics (e.g. the input impedance, or reflection properties) of the at least one powered electrical resonator may be monitored in order to locate the target device.
The method may comprise using a model to simulate the propagation of MIWs in the structure to determine how to adjust the parameters of the metamaterial structure to improve power transfer.
The system controller may comprise a model that simulates the propagation of MIWs in the structure. Once the target resonator has been identified, the system controller may use the model to determine how to increase current flow at the target resonator.
The system controller may select an appropriate method for achieving this from those disclosed herein.
Adjusting the parameters of the metamaterial structure may comprise adjusting a location and/or phase of a further powered electrical resonator, wherein the location and or/phase of the further powered electrical resonator is selected to provide constructive interference at the one or more target resonator.
Adjusting the parameters of the material structure may comprise adjusting the frequency of the alternating current.
The phase of the at least one powered electrical resonator and the further powered electrical resonator may be different.
The adjusting at least one of the electrical resonators may be periodic, to create successive patterns of standing waves that increase the average uniformity of current flow through the target resonators.
Improving power transfer may comprise at least one of:
According to a third aspect, there is provided a metamaterial structure comprising a plurality of electrical resonators that support magnetoinductive waves, wherein the electrical resonators comprise a first resonator type and a second resonator type arranged in an alternating pattern, the first resonator type having a larger extent than the second resonator type, and the wherein the structure is configured and excited with an alternating electrical current at one or more of the resonators to produce a current distribution in the structure with an the intensity pattern corresponding with a checkerboard, wherein the resonators of the first type are high current resonators, and the resonators of the second type are low current resonators.
The plurality of resonators may support dispersive magnetoinductive waves.
The resonators may be arranged in an array with a square or rectangular unit cell. The second resonators may be placed in the interstices of the first resonators.
The first resonator type may be octahedral, and the second resonator type may be square.
The first and second resonators may have the same nominal resonant frequency.
According to a fourth aspect of the invention, there is provided a system for wireless power communication, comprising a plurality of elements, including:
The system according to the first or third aspect may be provided with the features of the fourth aspect. The plurality of electrical resonators of the first, second or third aspect may be provided in the power transfer elements of the fourth aspect.
Features described with reference to the fourth aspect are applicable to the first and second aspect of the invention. For example, the features of the control device that are described in relation to the fourth invention are applicable, in isolation of the other features of the fourth aspect (such as elements being disposed on different substrates), to the first and second aspect.
The plurality of elements may be provided on at least two, or at least three substrates (or tiles). For example, each power transfer element may be provided on a separate substrate (or tile).
Where the system comprises a plurality of separate substrates, the system may be operable to provide wireless power to a target device brought into proximity with a power transfer elements (or any of the power transfer elements) once the substrates are brought into proximity to form the medium.
The input element may be configured to receive power by electromagnetic induction. In other embodiments the input element may be provided with an electrical connector for receiving a wired DC or AC power input (e.g. 2.4V, 5V, 7.2V, 12V, or 110V, 230V, 240V etc).
Each of the plurality of elements may be provided on a separate substrate, such as a printed circuit board (PCB).
The substrate may be flexible (e.g. polyimide/kapton) or rigid (e.g. fibre reinforced composite/FR4). In some embodiments, more than one element may be provided on a single substrate. For example, a substrate may comprise two, three or more power transfer elements, or a substrate may comprise one or more power transfer element with the/an input element.
The electrical resonator of each of the plurality of elements may have a Q of between 50 and 500 (as measured when disconnected from a power supply or load).
Configuring the system to form a medium supporting magnetoinductive waves may comprise placing at least some (or all) of the substrates next to each other.
The electrical resonator of each element (input, output, intermediate) may comprise at least one conducting loop and at least one capacitor (e.g. a split-ring type electrical resonator). The conducting loop may follow the edge of the substrate, having the same shape as the substrate.
When the system is configured to form a medium supporting magnetoinductive waves, the coupling coefficient between the resonators of adjacent elements may be at least 0.025 (where the coupling coefficient is defined as the ratio of mutual inductance between adjacent electrical resonators and the geometric mean of the self-inductance of each of the adjacent electrical resonators), or at least 0.05, 0.1, or 0.2.
The input element may receive power from a Rezence/Air Fuel compliant power transmitter unit. Each power transfer element may be operable to provide power to a Rezence/Air Fuel compliant power receiver unit.
The resonant frequency of the electrical resonator of each of the plurality of elements may be between 6 and 7 MHz (e.g. 6.78 MHz). The resonant frequency of the electrical resonator of each element may be nominally equal to a design frequency of the system.
The operating bandwidth may be at least 20% of the resonant frequency.
The width and length of each of the elements may be between 5 cm and 20 cm.
At least one of the plurality of elements may be controllable elements which further comprise a control device. The electrical resonator of each controllable element may be a primary resonator, and the control device may further comprise an active control component that is configured to adjust the impedance of the primary resonator of the controllable element in response to a control signal.
The control device may be operable to adjust the impedance of the primary resonator at a design frequency. The control device may be operable to adjust the impedance over a range of frequencies (i.e. to adjust the frequency response of the primary resonator).
The control device may be inductively coupled to the primary resonator. The control device may be conductively and/or capacitively coupled to the primary resonator. The control device may comprise an active control component that is conductively or capacitively coupled to the primary resonator and an active control component that is inductively coupled to the primary resonator (e.g. in a secondary resonator)
The control device may comprise a secondary resonator, inductively coupled to the primary resonator. The active control component may be arranged to vary the electrical properties of the secondary resonator in response to the control signal.
The coupling between the first and second resonator means that the coupled system will have two modes: a first mode in which the currents in the primary and secondary resonator are in phase, and a second mode in which the currents in the primary and secondary resonator are out of phase. The secondary resonator may be operable to cause an anti-resonance in the impedance of the primary resonator at the resonant frequency of the uncoupled secondary resonator. Using an active control component to change the properties of the secondary resonator may result in a change in the modes of the coupled system, thereby changing the effective impedance of the primary resonator (e.g. at the design frequency).
The secondary resonator may comprise a capacitor, and the active control component may be arranged in series with the capacitor.
The secondary resonator may comprise a capacitor, and the active control component may be arranged in parallel with the capacitor.
The secondary resonator may have a resonant frequency that is matched to a resonant frequency of the primary resonator to within 1%, 2%, 5%, or 10%.
The control device may comprise an inductor and the active control component may be in series with the inductor and operable to vary the effective resistance of the control device in response to the control signal.
The control device may comprise an inductor, and the active control component may be in parallel with the inductor and operable to vary the effective inductance of the control device in response to the control signal.
The control device may comprise a further active control component in parallel with the inductor, and the control device may be operable to vary the effective inductance of the control device in response to the control signal.
The active control component may be conductively coupled to the primary resonator.
The active control component may comprise a transistor, such as a MOSFET.
The active control component may comprise a variable capacitor, arranged to vary a resonant frequency of the primary resonator (e.g. by varying the capacitance of the primary resonator).
The active control component may be connected in series with a capacitor of the primary resonator, and may be operable to vary the effective resistance of the primary resonator in response to the control signal.
The control device and corresponding primary resonator of the at least one controllable cell may be disposed on different substrates.
The secondary resonator may be substantially concentric with the primary resonator. The secondary resonator may be substantially coplanar with the primary resonator.
The secondary resonator may be offset from the primary resonator in a direction having a component parallel with an axis of the primary conducting loop (e.g. in a direction along the axis).
The control device may be disposed on a different substrate to the primary resonator, and the controllable element may comprise a stacked combination of a substrate on which the primary resonator is disposed, and a substrate on which the secondary resonator is disposed.
The medium may comprise a plurality of controllable elements, arranged in a two-dimensional array. The active control component of each controllable element may be individually addressable, for instance by wireless communication.
At least some of the plurality of elements may comprise a power converter, operable to convert AC electrical power from the electrical resonator to DC power. At least some of the plurality of elements may comprise a controller, powered by the DC power.
The controller may comprise a receiver for receiving data wirelessly from at least one other element of the system.
The receiver may be configured to receive data propagated by modulated magnetoinductive waves propagating through the electrical resonators of the plurality of elements.
Each controllable element (e.g. controllable input element, controllable output element, controllable intermediate element) may comprise a power converter and a controller.
The controller may be configured to provide the control signal (to the control device) in response to the data received wirelessly.
The controller may further comprise a transmitter for transmitting data wirelessly to at least one other element of the system.
The transmitter may be configured to wirelessly transmit data to other elements by modulating magnetoinductive waves propagating through the electrical resonator of the element that includes the transmitter.
The receiver and/or transmitter may be Bluetooth, Zigbee, and/or 802.11 compliant.
Each element may be configured with a unique identification code.
The system may be configured to form an ad-hoc network comprising the elements when the elements are configured to form a medium supporting magnetoinductive waves. The network may be a partial mesh network or a mesh network.
The active control components may be responsive to an electrical signal.
At least one element of the system may further comprise a display device, and the controller may be configured to control the display device
In another embodiment, the system may comprise a plurality of target devices, each target device comprising a display device configured to receive wireless power from one of the plurality of elements, and to be controlled by the controller of the element from which the display device receives wireless power.
According to a fifth aspect of the invention, there is provided a display comprising a plurality of elements, including, comprising:
an input element comprising an electrical resonator for receiving power from a power supply,
The plurality of elements may be provided on at least two, or at least three substrates, and the medium may be formed when the substrates are brought into proximity.
The controller of this aspect may include any of the controller features described above with reference to the first aspect. Similarly the display device may include any of the display device features described with reference to the first aspect.
The display devices (of any aspect) may be configured to form a composite display device, and the system may further comprise a system controller configured to provide instructions to each display device via the controller of each element powering (or comprising) a display device, so as to display a composite image or video on the composite display device.
At least one element may further comprise a sensor selected from: an image sensor, a vibration sensor, a light sensor, a temperature sensor and a current/voltage sensor.
The system further may further comprise a system controller configured to optimise power transfer through the medium (e.g. to one or more target devices) by varying the impedance of controllable elements.
The input element may comprise the system controller.
The system controller may comprise a model of magnetoinductive wave propagation through the medium, the system controller being configured to use this model to determine which controllable elements should be placed in a high impedance state for optimal power transmission to the target device (or target devices).
Embodiments will now be described, purely by way of example, with reference to the accompanying drawings, in which:
Referring to
The coupling is due to the proximity between the conductors of adjacent elements, and resulting near-field magnetic interactions. Contact between the tiles may not be necessary, and the elements 100 may form a medium suitable for propagating magnetoinductive waves when there are gaps between adjacent tiles. In other examples, at least partial overlap of adjacent tiles may be used to increase coupling.
Each of the adjacent elements may have a inductor that is matched with the inductor of each of the other elements (e.g. of the same layout). Each of the resonators may also have a matched capacitance, thereby producing a nominally identical resonant frequency.
Each of the resonators may be designed with a relatively high Q, for example at least 50, at least 100, or at least 200. The Q of a resonator relates to the losses of an oscillating current in the resonator—a greater resistance in the resonator results in higher losses and lower Q. In practice it may be difficult to reduce the effective resistance of the inductor loop. Practical trade offs between competing design parameters may limit the Q to a few hundred for a practical device.
Power is provided to one of the elements 100 from an external power supply 350. An element 100 that is configured to receive power from the external power supply 350 is termed an input element 150. The input element 150 may comprise a connector for receiving AC or DC power from an external power supply (in a wired connection), as schematically illustrated in
Intermediate elements 200 provide a medium for magnetoinductive waves (and hence power) to be transmitted from the input element 150 to an output element 250. The output element 250 is in proximity with a target device 300, which is itself configured to derive power inductively from the oscillating magnetic field of the output element 250. The output element 250 may be of the same design as the intermediate elements 200—the term output element is merely used to denote an element 100 that is providing power to a target device 300. The electrical resonator of the output element 250 may be termed the target resonator. Intermediate elements 200 and output elements 250 may be thought of a different use cases for the same type of element, which may more generally be referred to as a power transfer element. The magnetoinductive field associated with any elements in the system may be used to power an adjacent target device.
Each power transfer element may be disposed on a separate tile, and each may have nominally identical design (i.e. matched inductance and capacitance, and therefore matched resonant frequency). In the example of
An advantage of a system comprising separate tiles that couple sufficiently strongly to form a medium supporting magnetoinductive waves when placed in a 2D array is that such a system can be used to produce a relatively large area surface that can deliver electrical power to compatible wireless devices that are placed more or less anywhere on the surface. This is illustrated in
Although an example has been described in which each tile comprises a single element, this is not essential, and double element tiles/tiles (comprising two elements of any kind) and tiles with more than two elements are also envisaged.
For the sake of simplicity in this disclosure, capacitance, resistance and inductance are often depicted as lumped elements, but it will be appreciated that in a real system at least some of these may be distributed (at least to some extent). For instance, a conductor loop may have distributed self-inductance and resistance, and some distributed capacitance with any adjacent conductors (or ground plane).
An input element 150 configured for directly injecting current to the resonator 110 may further comprise drive electronics (not shown), which may include an impedance matching network between an AC supply (voltage or current) and the resonator 110.
The input element may further comprise a controller (e.g. processor or microcontroller), and may include control functionality (e.g. software/firmware) for configuring and optimally driving the array of elements coupled (magnetoinductively) thereto. More than one input element may be provided to feed a medium with magnetoinductive power. This may be appropriate for relatively large arrays (e.g. comprising more than 4, 5, 6, or 10 elements in extent).
The input element 150 may be powered by electromagnetic induction from a power supply 350 (as shown in
Referring to
Some systems include elements (e.g. power transfer elements) that are controllable. A controllable element comprises means for changing the electrical properties of the resonator thereof, so as to change the degree to which the controllable resonator participates as an element of the magnetoinductive medium. Under some circumstances, more optimal distribution of power through the array may be achieved by effectively disabling some elements of the array (e.g. by giving that element a high impedance or low Q at the resonant frequency).
An example of a controllable element 1000 is illustrated in
Using an inductively coupled control device 1200 avoids the need to interfere with the design of the primary resonator 1100. Adding tuning elements into the primary resonator 1100 may degrade the Q factor thereof, or reduce the mutual coupling between adjacent primary resonators of the waveguide.
Since the secondary resonator 1200 is inductively coupled to the primary resonator 1100, it contributes to the impedance thereof. Varying the resistance and capacitance of the control device 1200 therefore affects the impedance of the primary resonator 1100.
The impedance contribution Ze from the secondary resonator 1200 is given by:
Where Zm=Rm+j(ωLm−1/ωCm), and the impedance of the primary resonator Zp is given by:
Several possibilities for the control device 1200 can be considered. Where Rm is very large, the contribution Ze of the secondary resonator 1200 to the impedance Zp of the primary resonator 1100 will be very small. Where Rm is small, and LmCm=LC (i.e. the resonant frequencies of the primary and secondary resonators 1100, 1200 are matched), the effect of the secondary resonator will be to cause an anti-resonance (high impedance) in the impedance of the primary resonator 1100 at the resonant frequency ωc of the un-coupled primary resonator 1100 (ωc=1/√{square root over (LC)}). The coupled system of the primary and secondary resonator 1100, 1200 will have two resonant modes: a first mode in which the currents in the inductors 113, 123 of the primary and secondary resonator are in-phase, and a second in which these currents are out-of-phase. Tuning Rm allows the effect of the secondary resonator to be changed. For instance, the effect of a secondary resonator 1200 with matched frequency and a larger Rm would be to reduce the Q factor of the resonance of the primary resonator 1100.
Where Rm is small, and LmCm≠LC (i.e. the resonant frequencies of the primary and secondary resonators 1100, 1200 are not matched), the effect of the secondary resonator 1200 will be to cause two coupled modes of current oscillation with different frequencies.
Each controllable cell 1000 may comprise a primary resonator 1200, arranged concentrically with a secondary resonator of a control device 1200. The inductance and resistance of the primary resonator may be provided by a primary loop 114 which is a split-ring resonator. The split is bridged by a capacitance 112. More than one discrete capacitor may be used, which improves matching by averaging any capacitor variation. The secondary resonator may be within the primary resonator 1100, and comprises a similar split ring resonator arrangement with at least one discrete capacitor 122 bridging the split. Each secondary resonator further comprises an active control component 125, in the form a MOSFET transistor. There may be more than one such MOSFET transistor in parallel (which reduces resistance in the saturation state).
Placing the secondary resonator within the primary resonator 1100 has a number of advantages. This arrangement means that the secondary resonator does not affect the spacing or coupling between the primary resonators, while at the same time achieving good inductive coupling between the primary and secondary resonators. Furthermore, any coupling between different secondary resonators will be minimised.
The primary and secondary resonator may be nested square printed copper coils with surface mount capacitors and transistors. The secondary resonator may be provided on a separate tile that is overlaid on top of the tile that carries the primary resonator. This approach has the advantage of being able to convert a non-controllable element into a controllable element by simply stacking tiles together.
Some or all of the elements in a system may be controllable elements. A system in which each tile is controllable provides a maximum degree of flexibility in configuring the array, a sufficient degree of control over the propagation of magnetoinductive waves through the system may be achieved when only a subset of the elements are controllable.
At least some elements may comprise a transmitter and/or receiver. For example, a controllable element may comprise a receiver for receiving control instructions, instructing the controllable element to vary the impedance of the resonator 11 (e.g. so as to switch the element into and out of coupling with the medium). Any existing wireless technology may be used to provide wireless communication between tiles, for example ZigBee, Wifi, or Bluetooth.
In order to power active devices comprised within an element, the element may comprise a power converter, operable to derive power from the resonator of the element to power active devices of the element. A circuit diagram is shown in
Each controller in a system of elements may be configured with a unique identification code, so that communication intended for, or coming from, that controller may be conveniently identified by use of this identification code.
Although a diode rectifier is depicted in
Referring to
An element may comprise a display device 710 controlled by the controller 610, as shown in
Display elements may be the target devices. A power and data backplane comprising an array of power (and data) transfer elements may be provided, and a display layer comprising display elements provided, stacked on the power and data backplane. Each display element may be configured to receive power and data from the underlying power transfer element (or input element).
An element may comprise at least one sensor, as shown in
At least one element may be provided with power transfer monitoring sensors to detect and communicate when an element is loaded by a target device receiving power, so that the array can be reconfigured to provide optimal power transfer to the target devices (e.g. at maximal efficiency, or at maximum power transfer rate).
The system may further comprise a locator wand for setting up the system, allowing the locations of each tile to be identified during installation, using the wand. The wand may communicate with a system controller (which may be incorporated in an input tile) to identify the location of each element in an array of elements. The wand may, for example, allow the user to read the unique identification code of each element, so that the position of each tile can be recognised within an array by the system controller.
The system controller may comprise a model of magnetoinductive wave propagation through the medium, and the system controller may be configured to use this model to determine which tiles should be switched off (i.e. placed in a high impedance state so as not to participate in the medium) for optimal power transmission to the target device(s).
In order to illustrate ways in which the system controller could reconfigure a medium according to the invention to optimise power transfer, some discussion of power transfer within a medium in accordance with an embodiment will be described, with reference to
An electric current in one of the elements of the two-dimensional lattice will therefore excite currents in the neighbouring coils via magnetic/transformative coupling. This excitation will propagate in the lattice in a form of a magneto-inductive wave (MIW). These waves obey the dispersion law in relation to energy/frequency and direction of propagation, which strongly depends on the lattice geometry. When excited at or in the vicinity of the resonant frequency of the identical individual elements, fr, the MIW is forced to propagate in a very specific range of directions—symmetry axes of the Brillouin zone. In square lattices, MIW excited at frequencies close to fr, travel along kx=ky (as shown in
The ability of a metamaterial medium comprising a plurality of electrical resonators to collimate MIWs and convert them into narrow directive magneto-inductive beams (MIBs) can be used to help optimise power transfer in the context of an array of power transfer elements.
In order to illustrate this,
In the examples of
The linear dimensions of each tile was 10 cm; average resonance frequency 6.73±0:3% MHz; quality factor 232±1:7%; coupling coefficient of aligned, adjacent tiles ≈−0.07 (de ned as the ratio of mutual inductance to the self-inductance of the tiles).
In
In
A system comprising current sensors and controllable elements may optimise power distribution through an array by operating in an initialisation phase to determine the relationship between current distribution in the array and the state of controllable elements. A model of the relationship may be based on a simplified physical representation of the coupling between neighbouring resonators (e.g. nearest neighbour approximation). Alternatively, the model may comprise a neural network that has been trained during an initialisation phase to model the relationship. The model may comprise the locations of the elements, which may be provided to a system controller by a user (e.g. via a GUI, or using a locator wand).
In these examples defects in the array of resonators was created by removing a tile comprising a resonator, but equivalent results can be achieved by switching a resonator of a controllable element ‘off’, for example by using a secondary resonator (e.g. as discussed above).
The term metasurface may be used herein to mean a 2D MIW supporting medium. In the examples disclosed herein, an array of electrical resonators, each disposed on a tile, is used. Similar methods can also be used in 3D matamaterials, supporting 3D MIWs.
MIWs propagating along finite metasurfaces will form standing wave patterns. These patterns can be experimentally identified by scanning a near field probe across the metasurface to measure the induced magnetic field amplitude. Maxima of magnetic field amplitude, or “hot spots” (if strongly localised) correspond to locations of most efficient power transfer available on the metasurface. These are the locations where a wirelessly charging device would charge best. Field patterns will change if the frequency of excitation of the MIW changes—this can be especially pronounced near the resonant frequency of the resonators that form the matematerial. At a specific frequency (or range of frequencies), field patterns defining the location of magnetic field maxima depend on the geometry of the metasurface—its boundaries, degree of anisotropy, and degree of uniformity. These aspects of a metasurface can be tailored to control propagation of MIWs in the metamaterial to produce constructive interference at target locations.
The metamaterial may comprise different elements for controlling MIW propagation, including,
Any of the elements can be:
In general, mechanisms for MIW control can be considered to fall into the following categories:
Any of the effects described herein can be:
The methods described herein are applicable to MIWs propagating in metamaterials (such as metasurfaces) at frequencies close to the resonant frequency fr of each resonator, which will have strong spatial dispersion, and also to MIWs propagating at frequencies significantly different from fr, which will have weak spatial dispersion, with propagation similar to cylindrical waves). The principles disclosed herein can be applied to control MIWs that carry power and/or data—in either case, the efficiency with which current is coupled through the array is important. Cardinal terms such as N, S, E and W may be used to describe regions of arrays in this disclosure, with N corresponding with an upward direction with reference to the diagram. Such directions are relative, and do not specify a particular direction with respect to an external frame of reference.
In the examples, square lattices of electrical resonators are considered. The control methods described herein are also applicable to triangular and hexagonal arrays. The general approach of controlling constructive interference of MIWs to increase current flow in a target tile is applicable to any set of electrical resonators that support MIWs, including aperiodic or random assemblies of resonators. In the examples described herein, arrays of identical electrical resonators will be considered.
Arrays of Nx×Ny elements will be considered by way of example, where Nx,y are odd numbers and where the source tile is placed in the centre of the array, at element number (Nx+Ny+1)/2. The methods disclosed herein will of course work with arrays comprising an even number of elements in x and/or y, and with source resonators that are not located at the centre (e.g. at the edge, or plural source resonators).
Defects in the lattice may be created by electrical resonators that are either absent, switched off or detuned from the nominal design resonant frequency. Methods by which a switchable resonator (or a controllable element) can be implemented have already been discussed above. A switchable resonator may be one that is identical to the other resonators of the array when in an ‘ON’ state, and significantly different from the other resonators of the array when in an ‘OFF’ state. An ‘OFF’ state can be achieved by: physical removal; direct detuning or switching; detuning via a strongly-coupled additional resonator. In terms of circuit design, this switchability can be achieved through the use of FETs, relays, MEMS switches and other components with similar functionality.
In the examples provided, two different coupling regimes are considered: weakly-coupled arrays where only the next-nearest neighbours (adjacent tiles) are coupled; and strongly-coupled arrays where three next-nearest neighbours are coupled (adjacent, corner touching, and adjacent to adjacent).
The example numerical calculations and experimental data were obtained for tiles in which the shape of the electrical resonator's inductor is square (as shown in
The electrical parameters of the example resonator are: self-capacitance C0=5.43 pF (distributed over the inductor), resonator capacitance (lumped) Ca=188 pF, inductance L0=2.89 μH, quality factor Q=232, fr=6.73 MHz.
MIWs launched in 2D arrays of resonators reflect from the array borders, forming standing-wave patterns. These patters define tiles with high and low current intensity and, consequently, the ‘hot spots’ for efficient power-transfer (e.g. to a receiver is placed over one of the high-current tiles).
Parameters of the system are adjusted in order to tailor the current distribution profile across the tiles.
Engineered Border Profiles
The borders of 2D arrays (or a 3D array) can be engineered by creating a pattern or profile of defects in contact with an edge of the array to create specific standing MIW patterns. The profile of defects at the border can be implemented by either removing a set of resonators, adding a set of resonators or switching a set of resonators on or off (e.g. by detuning from their resonant frequency, or control of a secondary resonator).
This method may be especially important for operating frequencies close to the resonance frequency of individual tiles, because around that frequency, MIWs become strongly dispersive; the direction of their propagation is defined by the metasurface lattice geometry.
Referring to
A checkerboard excitation pattern can be achieved in a strongly coupled array by exciting the array at a frequency that is different than the resonant frequency fr.
Dynamic Field Patterns Using Temporally Periodic Switching
Dynamic control of standing MIW patterns is possible through periodically-switchable resonators. For example, for the system in
In this example, elements #21 and #25 will be switchable elements, as will each of elements #1 to #5. Both resonators #13 and #18 are configured to act as sources. Now, we can periodically control the elements as follows:
This alternating between which resonator is driven and which resonators are ‘on’ will result in a switching chessboard pattern, in which during period 1, odd resonators in the active region of the array are excited with good efficiency, and during period 2, even resonators in the active region of the array are excited with good efficiency. Periodically switching between the first and second period (e.g. with a 1:1 duty cycle) can be used to provide a spatially even distribution of power to the resonators. The rate at which such switching takes place can at any suitable rate: for example up to 10 KHz or as low as a 1 Hz. According to this approach, a device placed anywhere in the central region of the array may receive power with a good efficiency. Using this approach, it may not be necessary to locate a target resonator that provides best coupling to the target device.
Structured Lattice Defects and Lambda-Periodic Defects
This method may be particularly applicable to excitation of MIWs at or near to the resonant frequency of the resonators. At this frequency, the wavelength of the MIWs is equal to four resonators. Lattice defects may be introduced with a spatial period corresponding to the wavelength of the MIWs at the resonant frequency of the resonators. This may be termed a lambda-periodic defects. Such defects may be introduced across the array in a grid pattern (as shown in the example of
The configuration shown in
Pseudo-Uniform Field Profiles in Bi-Atomic Metamaterial Structures
Resonators configured as a metamaterial structure capable of supporting MIWs do not have to be identical. As already disclosed above, it possible to create a standing MIW checkerboard pattern of intensity. If even-numbered elements in an array are replaced with geometrically small electrical resonators, the area where wireless power transfer is inefficient as a fraction of the array area can be reduced. The geometrically small elements can be made electrically equivalent to the larger elements. One convenient configuration is octagonal resonators that are geometrically large, with square resonators in the interstices between the octagonal resonators that are small. This approach can be used to provide a relatively uniform efficiency of power transfer across the array.
Controlling MIWs to Generate Hotspots
A set of control methods is disclosed herein comprising manipulation (or adjustment) of resonators in a metamaterial structure, resulting in the generation of high current density (and correspondingly high magnetic field) in certain targeted areas of the structure (in contrast to approximating a uniform pattern throughout the structure). These methods can be employed to maximise power transfer to a target device located in proximity to a particular target resonator, at the same time as minimising energy loss in the rest of the resonators.
Pinball Approach
The intensity pattern in the resonators can be manipulated by controlling MIW scattering on defects in the lattice. Defects may be introduced using controllable elements, as described herein. As shown in
Holographic Borders
Controlling the defects at the edges of the array can be used to manipulate reflections from the edges. By changing the reflection profile from the edges/borders of the array, it is possible to re-direct MIW beams to create power-transfer ‘hot-spots’ in desired locations in the array. This is illustrated in
Excitation Control
The location, frequency and relative phase of power injection can be used to control the distribution of current density in the array.
It may be useful to place power injection resonators at the border of the array.
Quasi-1D Channels in Metasurfaces
A quasi-1D channel can be created in a metamaterial substrate by activating only a 1-dimensional path of resonators between the source (powered) resonator and the target resonator, which receives power. Power transfer may take place in more than one direction from a powered resonator.
If the receiver device presents a load that is strongly mismatched with the power-transmitting array, reflections may occur from the receiver device, resulting in less efficient power transfer. One way to improve impedance matching where this situation arises may be to add redundant spurs to the quasi-1D channel, which will change the effective impedance of the quasi 1D channel of the power transmitting array, and may improve matching with the receiver.
In some embodiments one or more elements may be provided with a communication system for interface with devices external to the system. The communication may (as already mentioned above) comprise a Bluetooth, Wifi or Zigbee system, or a wired connection such as Ethernet and USB.
It will be understood that each example of functionality for an element is not exclusive with other functionalities—a single element may comprise any or all of the functionalities described herein (e.g. a display element with a sensor, etc.). Furthermore each functionality described above may be implemented on a stackable tile, that is brought into communication and power coupling with the power transferring primary resonator by stacking the respective tile on the tile carrying the primary resonator.
With such an arrangement a modular system of tiles is possible. A power transmission medium can be constructed from simple power transfer elements, which may include only passive components, and which each include a primary resonator for transmitting magnetoinductive waves. Each power transfer element can be augmented by the addition of further tiles in a stacked configuration. A subset of the power transmission elements can be converted into a controllable elements by the addition of a controllable secondary resonator stacked with the primary resonator. A subset of the power transmission elements can be converted into power monitoring elements, for detecting and locating a target device drawing power from the system. The data from power monitoring elements may be used by a system controller to control the controllable elements so as to dynamically optimise power transfer through the system. At least some of the elements may be able to provide power to a target device that requires a different wireless power transfer standard, using a power converter and output inductive loop (which may also be provided in a stacked configuration with the basic power transfer element).
Although embodiments with separate substrates (or tiles) have been described, it is also possible to create a single substrate that includes an input element and a plurality of power transfer elements (i.e. with the resonators all on a single substrate).
Although specific embodiments have been described, variations are possible which are intentionally within the scope of the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| GB 1709627.2 | Jun 2017 | GB | national |
| GB 1719246.9 | Nov 2017 | GB | national |
This application claims priority under 35 U.S.C. § 120 as a continuation of U.S. patent application Ser. No. 16/621,476, titled MAGNETOINDUCTIVE WAVE CONTROL, filed Dec. 11, 2019, which is a U.S. National Stage Application and claims the benefit under 35 U.S.C. § 371 of PCT/GB2018/051640, titled MAGNETOINDUCTIVE WAVE CONTROL, filed Jun. 14, 2018, which claims priority to United Kingdom Application No. GB 1719246.9, filed Nov. 20, 2017, and United Kingdom Application No. GB 1709627.2, filed Jun. 16, 2017, which patent applications are all hereby incorporated herein by reference in their entireties for all purposes. The present application relates to a method of controlling magnetoinductive waves, and apparatus configured to control magnetoinductive waves. It would be convenient to be able to provide power to electronic devices without the need for a wired connection to a fixed power supply. The rapid growth of autonomous devices, such as mobile phones, tablets, laptops, household robots means that such technology is more relevant than ever. Most such autonomous devices are presently battery powered, and charging is often inconvenient. There are significant implications with large batteries, which impact cost and device weight, and which increase device size. A more convenient way of providing electrical power to devices would mitigate the need for large batteries, by improving the ease with which a device can be kept topped-up with charge. Furthermore, wired connections are potentially clumsy, and require manipulation of a connector fitted to the cable in order to electrically connect a device to a power supply. Power and connectors are furthermore notorious points of failure for electronic devices, either simply as a result of repeated cycles of connection and disconnection, or as a result of a trip or similar accident imposing a mechanical load on the connector via the cable. A significant amount of research and development has been undertaken in wireless power transfer. A number of standards exist for wireless power supply, including Rezence and Qi. Both systems employ a powered coil in a power transmission unit, and a further receiver coil in the device to be wirelessly powered. Qi systems have a relatively short range, and require relatively close proximity (e.g. 5 mm) inductive coupling between the powered coil and receiver coil. In Rezence systems a resonant inductive coupling between the powered coil and receiver coil is used to transfer power to the target device. The resonant coupling between the powered coil and receiver coil means that power can be transmitted over a greater distance. EP2617120 discloses wireless energy transfer systems in which repeater resonators are used to transfer power from a source resonator to a target area. At least one of the repeater resonators is detuned according to a routing algorithm. Although considerable progress in developing wireless power transfer has been made, considerable room for improvement exists.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16621476 | Dec 2019 | US |
| Child | 17740886 | US |
