Patent Publication Number: US-2019184842-A1

Title: Wireless charging with multiple charging locations

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to a U.S. non-provisional patent application entitled, “Device Authentication for Wireless Charging,” filed the same day as the instant application. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to batteries and charging systems, and in particular to wirelessly charging battery powered vehicles. 
     BACKGROUND INFORMATION 
     Battery powered devices such as drones, robots, submarines, satellites, electric cars, electric trucks, electric bikes, and other devices and vehicles may require battery charging. Wireless charging of these battery powered devices may offer reduced down-time and increase deployment efficiencies of the devices. Increasing the efficiency of the devices is desirable when more than one wireless charger is available to wirelessly charge a device or plurality of devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
         FIG. 1  is an example system that includes a plurality of wireless chargers and devices that can receive wireless energy from the wireless chargers to charge batteries of the devices, in accordance with an embodiment of the disclosure. 
         FIG. 2  illustrates an example wireless charger including a communication interface and a transmit charging coil to deliver wireless energy to a receive charging coil, in accordance with an embodiment of the disclosure. 
         FIG. 3  illustrates an example device that includes a wireless communication interface, a receive charging coil, and a propulsion mechanism, in accordance with an embodiment of the disclosure. 
         FIG. 4  illustrates an example system that includes a wireless charger and a device configured to receive wireless energy from the wireless charger, in accordance with an embodiment of the disclosure. 
         FIG. 5  illustrates a flow chart of an example process of identifying a wireless charger availability to charge a vehicle, in accordance with an embodiment of the disclosure. 
         FIG. 6  illustrates a flow chart of an example process of dual-band communication for authenticating a device for wireless charging, in accordance with an embodiment of the disclosure. 
         FIG. 7  illustrates a system including a wireless power transmitter and a wireless energy receiving module including a receive charging coil, in accordance with an embodiment of the disclosure. 
         FIG. 8  includes an example impedance network, in accordance with an embodiment of the disclosure. 
         FIG. 9  illustrates a flow chart of an example process of authentication for wireless charging, in accordance with an embodiment of the disclosure. 
         FIG. 10  illustrates an example quadcopter having a receive charging coil, an example transmit charging coil included in a charging mat, and a charger coupled to drive the transmit charging coil, in accordance with an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of a system, apparatus, and method of identifying wireless charging availability and authenticating devices for wireless charging are described herein. In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Throughout this specification, several terms of art are used. These terms are to take on their ordinary meaning in the art from which they come, unless specifically defined herein or the context of their use would clearly suggest otherwise. 
     Many electronic devices include a battery that can be charged and recharged. Many times, the battery of the device is recharged by connecting the device to a charger with a charging wire. With conventional manual or mechanical re-charging, a mechanical connection is required to plug the device in for charging, and the physical connection comes apart when charging is complete. Automatically making and breaking mechanical connections has the following problems: (1) it is unreliable (often the operation fails due to sensing or actuating errors); (2) it leads to wear of contacts/connectors, which fail after a certain number of plug/unplug cycles; (3) it adds cost and complexity to the system, since some form of robot arm, human intervention or mechanical contact is needed to accomplish the plugging and un-plugging (and often these mechanisms must produce large amounts of force, adding to its cost and complexity); and (4) the additional mechanical parts in the charging mechanism are a further source of system-level unreliability, as the exposed ohmic contacts are prone to corrosion and are affected by water and humidity due to the environmental conditions. Thus, some contexts benefit from wirelessly charging a device to reduce human intervention and increase reliability. 
     In a particular illustrative context, drones used in aerial photography, are typically human supervised. When the drone runs out of power, a person plugs the drone into a charger. To enable new, autonomous drone applications, such as unattended, automatic daily inspection of a field or bridge, with the human operator absent, it is desirable for drones to be able to charge themselves. 
     In some system implementation, there may be a plurality of devices and a plurality of wireless chargers for charging those devices. When the devices are also vehicles having propulsion to navigate to the wireless chargers to gain contactless power, the system may improve efficiency from coordinating the charging of the devices at particular wireless chargers. In embodiments of the disclosure, a wireless charger may provide charging station data that allows the devices to locate the wireless charger to receive contactless power. The charging station data may also provide intelligence, such as a charging status of the wireless charger, so that the device will have charging availability of a particular wireless charger. The devices may navigate to a wireless charger based on the location of the wireless charger and/or the charging availability of the wireless charger. The device may receive the charging station data (e.g. location and/or charging availability) of more than one wireless charger and select and navigate to one of the plurality of wireless chargers based at least in part on the charging station data. 
     Emerging applications that may benefit from the disclosure include aerial, mobile, and aquatic robots. “Drones” are aerial vehicles, typically quad-copters with  4  (or more) electrically driven rotors. Aerial vehicles can also be embodied by fixed-wing unmanned aircraft driven by electrical motors. Conventional drones may typically operate for 10 minutes to 40 minutes before needing to recharge. Mobile robots drive along a surface using one or more electric motors to drive wheels and move the device. Mobile robots are used in many consumer, industrial, medical, retail, defense and security applications today. Aquatic robots drive above or below the surface of water using turbines or buoyancy pumps to propel the device in three-dimensional space. All of these types of robotic devices typically have batteries on the device that need to be recharged. Of course, devices such as forklifts, golf carts, electric vehicles, autonomous vehicles, and other devices may also benefit from wireless charging to receive contactless power in accordance with embodiments of this disclosure. 
       FIG. 1  is an example system  100  that includes a plurality of wireless chargers  111  and devices  101  that can receive wireless energy from the wireless chargers  111  to charge batteries of the devices  101 , in accordance with an embodiment of the disclosure.  FIG. 1  includes wireless chargers  111 A,  111 B, and  111 C (collectively referred to as wireless chargers  111 ) and devices  101 A,  101 B, and  101 C (collectively referred to as devices  101 ). Device  101 A is an aerial drone, device  101 B is an electric car, and device  101 C is a land-based robot. Electric car  101 B may be an autonomous car in some embodiments. Of course, system  100  may include a plurality of devices  101 A,  101 B, and/or  101 C and other devices or vehicles could be included in system  100 . 
     In embodiments of the disclosure, wireless chargers  111  may “broadcast” charging station data for use by devices  101 . The charging station data may include a location of the wireless charger or a charging station identifier that can be used to identify a location of the wireless charger. The charging station data may also include charging availability data of the wireless charger. For example, if the wireless charger is presently charging a device, this may be reflected in the charging availability data so that device(s)  101  will be informed that a particular wireless charger is currently occupied. The devices  101  may receive the “broadcast” from a plurality of wireless chargers and then navigate to a particular wireless charger from the plurality of wireless chargers based at least in part on the data provided in the broadcasts from the plurality of wireless chargers. The devices may also take into account wind data, geographical data, and remaining battery capacity of the device, for example. 
     In  FIG. 1 , wireless charger  111 A broadcasts via communication channel  142 A, wireless charger  111 B broadcasts via communication channel  142 B, and wireless charger  111 C broadcasts via communication channel  142 C. Also in  FIG. 1 , device  101 A receives data via communication channel  141 A, device  101 B receives data via communication channel  141 B, and device  101 C receives data via communication channel  141 C. In some embodiments, the broadcast(s) of the wireless chargers  111  are relayed to the devices  101 A via a communication network  103 . Communication Network  103  may include any network or network system such as, but not limited to, the following: a peer-to-peer network; a Local Area Network (LAN); a Wide Area Network (WAN); a public network, such as the Internet; a private network; a cellular network; a wireless network; a wired network; a wireless and wired combination network; and a satellite network. 
     Communication channels  141  and  142  may include or be routed through one or more wired or wireless communication utilizing IEEE 802.11 protocols, Bluetooth, SPI (Serial Peripheral Interface), I 2 C (Inter-Integrated Circuit), USB (Universal Serial Port), CAN (Controller Area Network), cellular data protocols (e.g. 3G, 4G, LTE, 5G), optical communication networks, Internet Service Providers (ISPs), a peer-to-peer network, a Local Area Network (LAN), a Wide Area Network (WAN), a public network (e.g. “the Internet”), a private network, a satellite network, or otherwise. 
     In one illustrative embodiment, one or more wireless chargers  111  utilize an Ethernet connection as communication channel  142  and “broadcast” charging station data to a server  122  that is included in communication network  103 . Server  122  computer may be located remotely in a data center or located local to the wireless charger  111 . Server  122  may then send the data to the device(s)  101  via cellular network  121  or satellite network  123 , for example. Of course, when device(s)  101  receive the charging station data from a satellite, communication channel  141  is satellite communication channel and when device(s)  101  receive the charging station data from a cellular tower, communication channel  141  is a cellular communication channel. 
     In one embodiment, server  122  may aggregate charging station data from multiple wireless chargers  111  and forward the aggregated data to devices  101 . In one embodiment, server  122  may filter the charging station data by location of the wireless charger and only forward to the devices  101  the charging station data from wireless chargers that are within a certain distance of the device. The device may report a location (e.g. GPS location) to the server  122  for the purposes of filtering the charging station data that is forwarded to the device  101 . For example, a device may only receive charging station data for wireless chargers  111  that are within 5 miles of the device. Of course, other distances may be used as a filter. 
     In one illustrative embodiment, one or more wireless chargers  111  use a cellular communication channel  142  to “broadcast” charging station data and the charging station data is received by the device(s)  101  on a cellular communication channel  141 . 
     In one illustrative embodiment, wireless charger(s)  111  communicate directly with devices  101  and communication network  103  is not utilized. Rather, wireless charger(s)  111  may broadcast a wireless signal that is received by devices  101 . For example, wireless charger  111  may broadcast a WiFi signal on communication channel  142  and that same WiFi signal may be received directly by device(s)  101 . In some embodiments, the device(s)  101  may initiate an initial handshake to establish wireless communications with the wireless charger(s)  111  before the wireless charger(s)  111  “broadcast” their charging station data to the device(s)  101 . In other embodiments, the wireless charger(s)  111  may initiate an initial handshake to establish wireless communication with the device(s)  101  before the wireless charger(s) “broadcast” their charging station data to the device(s)  101 . 
       FIG. 2  illustrates an example wireless charger  211  including a communication interface  220  and a transmit charging coil  205  to deliver wireless energy to a receive charging coil, in accordance with an embodiment of the disclosure. Wireless charger  211  includes wireless power transmitter  209  that includes a driver  207  coupled to the transmit charging coil  205 . Driver  207  drives a signal onto transmit charging coil  205  to facilitate wireless energy delivery to a receive charging coil configured to receive the wireless energy. The receive charging coil may be included in or attached with a device  101 . Wireless charger  211  also includes processing logic  243 , location sensor  257 , sense module  253 , and memory  251 . Memory  251  may store a charging station identifier of the wireless charger  211  and other data and/or instructions for execution by processing logic  243 . 
     Processing logic  243  is coupled to wireless power transmitter  209 . Processing logic  243  may control driver  207  to adjust the output of transmit charging coil  205 . Processing logic  243  is communicatively coupled to location sensor  257 , in  FIG. 2 . In one embodiment, location sensor  257  is a global positioning satellite (GPS) sensor providing GPS coordinates to processing logic  243 . Processing logic  243  is also communicatively coupled to sense module  253  in  FIG. 2 . Sense module  253  may include one or more proximity sensors, image sensors, or thermal cameras. The proximity sensor, image sensors, or thermal cameras may be positioned to detect the presence of humans, animals, or interfering objects. When a human, animal, or interfering object is sensed, processing logic  243  may disable the wireless charging of wireless charger  211  for safety purposes. Sense module  253  may also detect the presence of a proximate device that is being charged by wireless charger  211 . When a device is currently being charged by wireless charger  211 , processing logic  243  may update charging availability data of the charger  211  to reflect the charging availability of the wireless charger  211 . 
     Processing logic  243  is communicatively coupled to communication interface  220 . Communication interface  220  may include one or more separate communication interfaces. Communication interface  220  may include wired (e.g. Ethernet) and wireless (e.g. WiFi, cellular, Bluetooth, and/or RFID) communication interfaces. In the illustrated embodiment, communication interface  220  includes a wireless interface  223  configured for IEEE 802.11 communication and a radio frequency identification (RFID) interface  225 . RFID interface  225  may include an RFID “reader” that transmits RFID challenge signals. Communication interface  220  may send and receive data via one or more communication channels  242 . Wireless charger  211  may send and/or receive data  273  (e.g. charging station data) via communication channel  242 . In some embodiments, communication channel  242  is a wireless communication channel using a time division multiple access (TDMA) protocol to communicate with multiple devices and performs a clear-channel-assessment to ensure that the wireless communication channel  242  is not already occupied by other proximate communication systems (e.g. WiFi or remote control). This allows multiple devices to communicate with charger  211 , if needed. 
       FIG. 3  illustrates an example device  301  that includes a wireless communication interface  320 , a receive charging coil  303 , and a propulsion mechanism  384 , in accordance with an embodiment of the disclosure. Device  301  also includes a wireless energy receiving module  393 , a battery  395 , a memory  307 , a measurement module  330 , and a location sensor  353 . Battery  395  may include multiple battery cells. In one example, battery  395  includes six battery cells. Battery  395  may include lithium-ion, nickel cadmium, or other battery chemistry. Wireless energy receiving module  393  includes a receive charging coil  303 , rectifier circuitry  315 , and power regulator  335 . Wireless energy received by receive charging coil  303  is rectified by rectifier  315  and regulated by power regulator  335  to charge battery  395  in the illustrated wireless energy receiving module  393  of  FIG. 3 . Rectifier  315  may include a full-wave bridge rectifier and power regulator  335  may include a PMIC (power management integrated circuit) such as a linear regulator, switching power supply, and/or switching regulator. 
     Processing logic  313  is coupled to wireless energy receiving module  393 . Processing logic  313  may control wireless energy receiving module  393  to adjust the charge/discharge of battery  395 . Additionally, processing logic  313  may receive electrical measurements from wireless energy receiving module  393 . Processing logic  313  is also coupled to measurement module  330  that may measure a voltage or a current of battery  395 . Measurement module  330  may include an analog-to-digital converter coupled to measure the voltage of battery  395  and/or a voltage representative of a current of battery  395 . Memory  307  is communicatively coupled to processing logic  313  in  FIG. 3  and processing logic  313  may read and write to memory  307 . Data and instructions to be executed by processing logic  313  may be stored in memory  307 . Location sensor  353  is coupled to processing logic  313  to provide a location of device  301 . In one embodiment, location sensor  353  is a GPS sensor and provides GPS coordinates to processing logic  313 . 
     Processing logic  313  is communicatively coupled to communication interface  320 . Communication interface  320  may include one or more separate communication interfaces. Communication interface  320  may include wired (e.g. Ethernet) and wireless (e.g. WiFi, cellular, Bluetooth, and/or RFID) communication interfaces. In the illustrated embodiment, communication interface  320  includes a wireless interface  323  configured for IEEE 802.11 communication and a radio frequency identification (RFID) interface  325 . RFID interface  325  may include an RFID “tag” that generates an RFID response signal when queried by an RFID challenge signal from an RFID reader. Communication interface  320  may send and receive data via one or more communication channels  341 . Device  301  may send and/or receive data  372  (e.g. charging station data) via communication channel  341 . 
     Propulsion mechanism  384  is coupled to be driven by processing logic  313 . Processing logic  313  may drive propulsion mechanism  384  based on data received from communication interface  320 , measurements of wireless energy receiving module  393 , and/or locations provided by location sensor  353 . Propulsion mechanism  384  may include one or more propellers for flight or underwater navigation. Propulsion mechanism  384  may include wheels and corresponding transmission or torque conversion hardware in the case of electric vehicles, for example. In some embodiments, propulsion mechanism may include tracks in the context of forklifts or land-based robots for example. Other propulsion mechanism examples may be used in accordance with embodiments of this disclosure. 
     The term “processing logic” (e.g.  243  or  313 ) in this disclosure may include one or more processors, microprocessors, multi-core processors, and/or Field Programmable Gate Arrays (FPGAs) to execute operations disclosed herein. In some embodiments, memories (not illustrated) are integrated into the processing logic to store instructions to execute operations and/or store data. Processing logic may include analog or digital circuitry to perform the operations disclosed herein. A “memory” or “memories” (e.g.  251  or  307 ) described in this disclosure may include volatile or non-volatile memory architectures. 
       FIG. 4  illustrates an example system  400  that includes wireless charger  211  and device  301  configured to receive wireless energy from the wireless charger  211 , in accordance with an embodiment of the disclosure.  FIG. 4  shows that wireless charger  211  may communicate with device  301  via communication channels  443 ,  444 , and/or  445 . In some embodiments, all three of communication channels  443 ,  444 , and  445  are utilized. Transmit charging coil  205  may deliver wireless energy  457  to receive charging coil  303 . Wireless power transmitter  209  may be driven by processing logic  243  to selectively transmit the wireless energy  457  to receive charging coil  303  as a technique to encode data in the transmission of wireless energy  457 . Similarly, wireless energy receiving module  393  may be driven by processing logic  313  to selectively reflect the wireless energy  457  as reflected wireless energy  456  and encode data into the reflected wireless energy  456 . Hence, communication channel  445  may include one-way and/or two-way communication between wireless power transmitter  209  and wireless energy receiving module  393 . 
       FIG. 5  illustrates a flow chart of an example process  500  of identifying a wireless charger availability to charge a vehicle, in accordance with an embodiment of the disclosure. The order in which some or all of the process blocks appear in process  500  should not be deemed limiting. Rather, one of ordinary skill in the art having the benefit of the present disclosure will understand that some of the process blocks may be executed in a variety of orders not illustrated, or even in parallel. 
     In process block  505 , a wireless charger (e.g. wireless charger  211 ) determines a charging status of the wireless charger. Determining a charging status may include processing logic  243  receiving a status signal from sense module  253  that indicates whether a vehicle is currently being charged by wireless power transmitter  209 . The charging status of wireless charger  211  may be updated to indicate that a vehicle is being charged based on the status signal from sense module  253 . The status signal may be activated based on signals from the sensors included in sense module  253 . In one embodiment, determining a charging status includes measuring one or more electrical characteristics of an amplifier providing a signal to transmit charging coil  205 . An amplifier using significant power may indicate ongoing wireless charging and thus the charging status may be updated to indicate that a vehicle is being charged. In one embodiment, determining a charging status includes driving a challenge signal onto an RFID interface included in communication interface  220 . If a valid response from an RFID tag is received by the RFID interface, a vehicle having the RFID tag is proximate to wireless charger  211 . 
     In process block  510 , the wireless charger transmits its charging station data to vehicles. As described with respect to  FIG. 1 , the transmission of charging station data may include broadcasting the charging station data on different communication channels. The charging station data may include a location (e.g. GPS coordinates) of the wireless charger and/or a charging station identifier. The charging station data may also include a charging status of the wireless charger. 
     In process block  515 , a vehicle receives the charging station data. The charging station data may be received by the vehicle via a wireless communication channel  141 / 341 . 
     In process block  520 , a location of the wireless charger is determined by the vehicle based on the charging station data. If the charging station data includes a charging station identifier, the charging station identifier may be used by the vehicle to ascertain the location of the wireless charger. A relational database may have locations of wireless chargers corresponding to the charging station identifier, for example. The relational database may be stored in a memory of the vehicle (e.g.  307 ) or be stored remotely and access by the vehicle using communication interface  320 , for example. If the charging station data includes GPS coordinates, for example, the location of the wireless charger can be determined from the GPS coordinates. 
     In process block  525 , the propulsion mechanism (e.g.  384 ) of the vehicle is driven to navigate the vehicle to the wireless charger based at least in part on the charging status and the location of the wireless charger. In one embodiment, driving the propulsion mechanism to navigate the vehicle includes driving the vehicle to the wireless charger when the charging status indicates a charging availability to deliver wireless energy to the receive charging coil of the vehicle. If the charging status of the wireless charger indicates that the wireless charger is charging another vehicle, the vehicle may not navigate to that wireless charger. In one embodiment, the vehicle navigates to the closest wireless charger that is unoccupied (not currently charging another vehicle). In one embodiment, the propulsion mechanism may be driven to navigate to a particular wireless charger based on the location of the wireless charger, the charging status of the wireless charger, and/or a battery voltage of the vehicle. If the battery voltage of the vehicle is particularly low and the range of the vehicle is therefore limited, the vehicle may navigate to the closest wireless charger even though the wireless charger is currently charging another vehicle, for example. 
     In process block  530 , the vehicle receives wireless charging from the wireless charger and in process block  535 , the wireless charger provides wireless energy to the vehicle. Of course, process blocks  530  and  535  may happen contemporaneously. 
     In process block  540 , the vehicle updates its charging status to indicate that it is currently charging a vehicle. In process block  545 , the wireless charger transmits charging station data that includes its updated charging status to vehicles. The charging station data may be transmitted by the communication interface  220 . 
     In one embodiment, process  500  further includes the vehicle transmitting, with a wireless communication interface, a navigation message to the wireless charger. This transmission may occur subsequent to process block  520  being executed. The navigation message may indicate that the vehicle is navigating toward the wireless charger for wireless charging. The wireless charger may receive the navigation message from the vehicle. In response to receiving the navigation message from the vehicle, the wireless charger may transmit queue data that includes a number of vehicles that are navigating toward the wireless charger. Providing queue data to vehicles via this transmission may allow the vehicles to determine a preferable wireless charger to navigate to. For example, if the queue data from a first wireless charger indicates that six vehicles are navigating to a first wireless charger while queue data from a second wireless charger indicates only two vehicles are navigating to the second wireless charger, this may factor into a navigation decision by the vehicle. 
     As described briefly above, each vehicle may receive charging station data from a plurality of wireless chargers and a vehicle may determine which wireless charger to navigate to for wireless charging based on receiving the charging station data from multiple wireless chargers. Hence, in one embodiment of process  500 , the vehicle may receive second charging station data that includes a second charging status of a second wireless charger. The vehicle may determine a second location of the second wireless charger and navigate the vehicle either to the first wireless charger or the second wireless charger based at least in part on the charging status and location of the first wireless charger and the second charging status and second location of the second wireless charger. The vehicle may receive charging station data from many (more than two) wireless chargers and select from among the many wireless chargers and navigate to the selected wireless charger based on the charging station data from all the many wireless chargers. 
     In one embodiment of process  500  where the vehicle is receiving charging station data from multiple wireless chargers, the initial charging station data include a first remaining charge time of a device being charged by the initial wireless charger and the second charging station data includes second remaining charge time of a device being charged by the second wireless charger. Here, even if two wireless chargers are at roughly the same distance from a vehicle and the charging status of each of the wireless chargers indicates they are currently charging a device, a remaining charge time of the device may assist the vehicle in determining which wireless charger to navigate to. The wireless charger (e.g.  211 ) may generate a remaining charge time from a battery voltage measurement of a vehicle being currently charged and reported to the wireless charger via the communication interface (e.g.  320 ) of the vehicle presently being charged. The battery voltage may be measured by a measurement module (e.g.  330 ) of the vehicle. In one embodiment, the wireless charger may generate a remaining charge time from a battery current measurement, battery state of health, battery state of charge, or battery capacity remaining of a vehicle being currently charged and reported to the wireless charger via the communication interface (e.g.  320 ) of the vehicle presently being charged. 
       FIG. 6  illustrates a flow chart of an example process of dual-band communication for authenticating a device for wireless charging, in accordance with an embodiment of the disclosure. The order in which some or all of the process blocks appear in process  600  should not be deemed limiting. Rather, one of ordinary skill in the art having the benefit of the present disclosure will understand that some of the process blocks may be executed in a variety of orders not illustrated, or even in parallel. 
     Wireless chargers servicing fleets of vehicles may need to authenticate whether a particular vehicle is authorized to be charged by the wireless charger. Various wireless communication protocols are vulnerable to being compromised by attacks from bad actors or even inadvertent access. Thus, authenticating schemes for authenticating devices and/or selecting devices for charging by wireless chargers may benefit from increased authentication and corresponding security. 
     In operation  603  of  FIG. 6 , a communication link is established between a wireless charger (e.g.  211 ) and a device (e.g.  311 ) configured to receive wireless energy from the wireless charger. In the example process  600 , operation  603  includes process blocks  605 ,  610 ,  615 ,  620 , and  625 . However, alternatives to the illustrated process blocks may be used to establish a communication link between a wireless charger and a device. 
     In the illustrated example operation  603 , process block  605  includes transmitting a data query with a wireless interface of the wireless charger. In process block  610 , the data query is received by a wireless communication interface of the device. In process block  615 , a data response is transmitted by the wireless communication interface of the device and in process block  620 , the data response is received by the wireless communication interface of the wireless charger. 
     In process block  625 , the device is verified by the wireless charger. Verifying the device may include checking the data response against a list of verified devices where the data response includes a device identifier. In one embodiment, verifying the device includes comparing the data response to an expected response from devices that are authorized to be charged by the wireless charger. In example process  600 , after the device is verified, process  600  proceeds to process block  630 . 
     In process block  630 , an authentication challenge signal is driven onto a transmit charging coil (e.g. transmit charging coil  205 ). The data query of process block  605  may be transmitted prior to the authentication challenge signal. In one embodiment, the data query is transmitted while the authentication challenge signal is driven onto the transmit charging coil. In one embodiment, driving the authentication challenge signal onto the transmit charging coil includes modulating at least one of a frequency or duty cycle of the authentication challenge signal. The authentication challenge signal may be driven within a second frequency range that is different from a first frequency range of the communication link established in operation  603 . In one embodiment, the authentication challenge signal is approximately 13.56 MHz and the communication link is approximately 2.4 GHz and utilizes IEEE 802.11 protocols. The authentication challenge signal driven onto the transmit charging coil may be approximately 13.56 MHz+/−7 kHz, 6.78 MHz+/−15 kHz, or 80-250 kHz. The communication link of operation  603  may utilize frequencies such as 400 MHz and 915 MHz. 
     In process block  635 , the device measures at least one electrical attribute of the authentication challenge signal received by a receive charging coil (e.g.  303 ) of the device. In one embodiment, the measured electrical attribute is a rectified voltage of the received authentication challenge signal on rectifier  315 . In one embodiment, the measured electrical attribute is a battery current supplied to charge a battery (e.g.  395 ) of the device. 
     In one embodiment, the authentication challenge signal is encoded with data and measuring the electrical attribute of the authentication challenge signal includes performing a series of measurements to decode data encoded into the authentication challenge signal. For example, a series of measurements of the rectified voltage can decode digital values encoded into the authentication challenge signal. 
     In process block  640 , the measured electrical attribute(s) are transmitted to the wireless charger as an authentication response signal with the wireless communication interface of the device. The authentication response signal indicates a receipt of the authentication challenge signals since the authentication response signal includes electrical attributes/measurements of the authentication challenge signal. 
     In process block  645 , the wireless charger initiates a wireless energy delivery from the transmit charging coil of the wireless charger to the receive charging coil of the device when the received measured attributes are within a pre-determined range. For example, if a rectified voltage is the measured electrical attribute, the measured attribute would need to be within a particular voltage range for verification purposes for the wireless charger to initiate a wireless energy delivery. The pre-determined range may be a digital value when the authentication challenge signal is encoded with digital data and the measured attribute includes the digital data decoded by the device. 
     Process  600  thus facilitates a dual-band authentication of devices that are presented for wireless charging since the authentication includes both wireless communication at the first frequency range in addition to some measurement of an authentication challenge signal of a second frequency range different from the first frequency range. The specific hardware required to measure the authentication challenge signal decreases the likelihood that the authentication scheme of process  600  will be compromised by a bad actor or inadvertent access to wireless charging would be granted. Advantageously, the dual-band authentication of process  600  utilizes the transmit charging coil of the wireless charger and the receive charging coil of the device that are already configured to send and receive, respectively, wireless energy. 
     In some embodiment, additional verification procedures are performed prior to wirelessly charging the device with the wireless charger. The additional verification procedures may include security and safety procedures. In one embodiment, an RFID tag on the device is also verified by an RFID reader of the wireless charger to provide further assurance that the proximate device is authorized to be receiving wireless charging from the wireless charger. 
       FIG. 7  illustrates a system  700  including a wireless power transmitter  741  and a wireless energy receiving module  793  including a receive charging coil  203 , in accordance with an embodiment of the disclosure. Example wireless power transmitter  741  may be included in wireless charger  211  and processing logic  243  may be coupled to control wireless power transmitter  741 . Wireless power transmitter  741  includes a driver  743  to generate a transmitter signal  744 . Amplifier  745  is coupled to receive the transmitter signal  744  from driver  743  and generate amplified transmitter signal  746  at an output of the amplifier  745 . Driver  743  may include a radio-frequency generator with a programmable amplitude, frequency or duty cycle. An amplifier voltage  732  and amplifier current  731  are provided to amplifier  745 . Voltage tuner  721  is coupled to adjust the amplifier voltage  732 . Voltage tuner  721  may include a switching power supply with a programmable voltage output. In one embodiment, voltage tuner  721  includes a programmable potentiometer that is controlled by processing logic (e.g.  243 ). In embodiments where voltage tuner  721  is a programmable potentiometer, one node of the potentiometer may be coupled to the amplifier voltage  732  and the other node may be coupled to amplifier  745 . In one embodiment, a digital-analog converter (DAC) is included in voltage tuner  721  to adjust the amplifier voltage  732 . The DAC may be coupled to receive digital values from processing logic (e.g.  243 ). Wireless power transmitter  741  also includes an impedance network  747  coupled to receive the amplified transmitter signal  746  and coupled to transmit an authentication challenge signal  748  onto transmit charging coil  205 . An impedance of the impedance network  747  may be adjusted to modulate the authentication challenge signal  748  that is driven onto transmit charging coil  205 . 
     The authentication challenge signal may also be modulated by adjusting the duty cycle, amplitude and/or the frequency of the transmitter signal  744  generated by driver  743 . In one embodiment, the authentication challenge signal may also be modulated by adjusting the amplifier voltage  732  provided to power amplifier  745 , which influences the magnitude of the authentication challenge signal. 
     Example wireless energy receiving module  793  includes receive charging coil  203 , an impedance network  763 , a rectifier  765 , and a power converter  767 .  FIG. 7  also includes a battery  395  having a battery voltage  772  and the battery  395  is coupled to the wireless energy receiving module  793 . Wireless energy receiving module  793  is an example wireless energy receiving module that may be included in device  301 . Impedance network  763  is coupled between receive charging coil  203  and rectifier  765 . Power converter  767  is coupled to generate converted voltage  768  and coupled to receive the rectified voltage  766  from rectifier  765 . One or more capacitors (not illustrated) and other filtering circuitry may be coupled to rectifier  765  to smooth rectified voltage signal  766 . Power converter  767  may include a linear regulator, switching power supply, or other dc-dc converters known in the art. 
     Wireless energy receiving module  793  also includes switches  753 ( 1 ),  753 ( 2 ), and  753 ( 3 ) coupled to receive converted voltage  768 . In  FIG. 7 , switches  753 ( 1 ),  753 ( 2 ), and  753 ( 3 ) are illustrated as transistors having gates  755 ( 1 ),  755 ( 2 ), and  755 ( 3 ), respectively. Gates  755 ( 1 ),  755 ( 2 ), and  755 ( 3 ) may be controlled by processing logic  313  when wireless energy receiving module  793  is included in device  301 . When switch  753 ( 1 ) is closed, battery current  771  charges battery  395 . In some embodiments, when switch  753 ( 2 ) is closed, converted voltage  768  is provided as device power  774  to a device that includes wireless energy receiving module  793 . When switch  753 ( 3 ) is closed, load  776  receives converted voltage  768 . In one embodiment, (not illustrated) the one or more of switches  753  are replaced with a conductor (e.g. copper trace) to provide converted voltage  768  directly to battery  395 , device power  744 , and/or load  776 . 
       FIG. 7  shows a signal  281  representative of an authentication challenge signal received by wireless energy receiving module  793 . The actual waveform of a received authentication challenge signal may be different in practice depending on how much filtering is applied to the signal. For illustrations purposes, a signal similar to signal  281  may be present as rectified voltage  766 . Processing logic (e.g.  313 ) may be coupled to sample the rectified voltage  766  at a given sampling time interval  783 . Processing logic  313  may include an analog-to-digital converter (ADC) to sample rectified voltage  766 . In one embodiment, a digital symbol is included in the authentication challenge signal. For signal  781 , the digital symbol may be the number 252 (binary 11111100) whereas the digital symbol for signal  782  may be 212 (binary 11010100). Processing logic that samples rectified voltage signal  766  may decode the digital symbol. An authentication response signal sent from device  301  to wireless charger  211  may include the digital symbol for authentication purposes, in some embodiments. The authentication response signal may be encoded into reflected wireless energy  456  and/or sent as data  372  via communication channel  341 . 
     In some embodiments, a time period t 1   785  that signal  781  is activated serves as the authentication challenge signals and the time period t 1   785  is measured by processing logic (e.g.  313 ) and the time period t 1   785  is included in the authentication response signal. In some embodiments, a magnitude of signal  781  serves as the authentication challenge signals and the magnitude of signal  781  is measured by processing logic (e.g.  313 ) and that magnitude is included in the authentication response signal. In some embodiments, the magnitude of an authentication challenge signal is measured at a plurality of moments in time and the plurality of measurements is included in the authentication response signal. 
       FIG. 8  includes an example impedance network  860 , in accordance with an embodiment of the disclosure. Impedance network  860  may be used as impedance network  747  and/or  763 , although impedance network  860  is illustrated for use with impedance network  747  in  FIG. 8 . Example impedance network  860  includes capacitors  851 ( 1 ),  851 ( 2 ), and  851 (N) coupled to receive amplified transmitter signal  746 , where “N” is the number of capacitors in impedance network  860 . In the illustrated embodiment, each capacitor  851  is coupled to a corresponding switch  853 . In  FIG. 8 , switches  853 ( 1 ),  853 ( 2 ), and  853 (N) are illustrated as transistors having gates  855 ( 1 ),  855 ( 2 ), and  855 (N), respectively. Gates  855 ( 1 ),  855 ( 2 ), and  855 (N) may be controlled by processing logic  243  when impedance network  860  is included in impedance network  747 . When a switch  853  is off (open), its corresponding capacitor  851  does not influence amplified transmitter signal  746 . However, when a switch  853  is on (closed), its corresponding capacitor  851  will influence amplified transmitter signal  746 . Therefore, turning on and off switches  853  (via gate voltages  855 ) will selectively add or subtract capacitance and thus influence amplified transmitter signal  746  that is driven onto transmit charging coil  205  as authentication challenge signal  748 . It is understood that impedance network  860  is an example for illustration purposes and that other impedance elements (e.g. resistors and inductors) can be used similarly to add or subtract impedance, in series or in parallel, to an impedance network to influence signal  746  and  748 . When impedance network  860  is included in impedance network  763 , gates  855 ( 1 ),  855 ( 2 ), and  855 (N) may be controlled by processing logic  313  to influence the impedance of receive charging coil  203 . 
       FIG. 9  illustrates a flow chart of an example process of authentication for wireless charging, in accordance with an embodiment of the disclosure. The order in which some or all of the process blocks appear in process  900  should not be deemed limiting. Rather, one of ordinary skill in the art having the benefit of the present disclosure will understand that some of the process blocks may be executed in a variety of orders not illustrated, or even in parallel. 
     In process block  905 , a wireless data channel is established between a first wireless communication interface (e.g.  223 ) included in a charger and a second wireless communication interface (e.g.  323 ) included in a receiving device. The particular technique for establishing the wireless data channel may vary. In one embodiment, the technique disclosed in operation  603  of  FIG. 6  is utilized. WiFi, Bluetooth, Zigbee, WirelessHART, and/or other protocols may be used for the wireless data channel. 
     In process block  910 , transmit circuitry (e.g.  721 ,  843   745 , and/or  747 ) included in the charger drives an authentication challenge signal onto a transmit charging coil included in the charger. The authentication challenge signal is included in wireless energy  456  in this embodiment. In one embodiment, driving the authentication challenge signal onto the transmit charging coil includes modulating at least one of a frequency, amplitude, or duty cycle of the authentication challenge signal. In one embodiment, driving the authentication challenge signal onto the transmit charging coil includes adjusting an amplifier voltage of an amplifier (e.g.  765 ) having an amplifier output coupled to the transmit charging coil. In one embodiment, driving the authentication challenge signal onto the transmit charging coil includes adjusting an impedance of an impedance network (e.g.  747 ) coupled to the transmit charging coil. In some embodiments, some combination of adjusting the amplifier voltage or current of the amplifier, adjusting the impedance of the impedance network, and adjusting the duty cycle, amplitude and/or frequency of the authentication signal is utilized to generate a unique authentication challenge signal. On the receiving device, measuring the rectified voltage (e.g.  766 ) and/or the battery current (e.g.  771 ) may assist in measuring the authentication challenge signal. 
     In process block  915 , at least one electrical attribute generated by the authentication challenge signal being driven onto the transmit charging coil is measured. The at least one electrical attribute may be measured while the authentication challenge signal is being driven onto the transmit charging coil. 
     In one embodiment, the at least one electrical attribute generated by the authentication challenge signals being driven onto the transmit charging coil is measured on the receiving device. Measuring the at least one electrical attribute generated by the authentication challenge signals being driven onto the transmit charging coil may include measuring a receiver electrical attribute of an electrical component coupled to a receive charging coil of the receiving device. The receiver electrical attribute may be transmitted from the second wireless communication interface of the receiving device to the first wireless communication interface of the charger. In one embodiment, the receiver electrical attribute is a rectified voltage (e.g.  766 ) from a rectifier (e.g.  765 ) coupled to the receive charging coil. 
     In one embodiment, the at least one electrical attribute generated by the authentication challenge signals being driven onto the transmit charging coil is measured on the charger. For example, the amplifier voltage  732  or amplifier current  731  may be measured as the at least one electrical attribute when an authentication response signal is generated by modulating the impedance of receive charging coil  203 . In other words, measuring amplifier voltage  732  or amplifier current  731  while the authentication challenge signal is being driven onto transmit charging coil  205  is one technique for measuring the authentication response signal when the authentication response signal is generated by impedance modulation of impedance network  763 , for example. In this embodiment, the receiving device (e.g.  301 ) may sense a signal on the receive charging coil  203 . Sensing a signal may include periodically sampling the rectified voltage  766  and comparing the sampling to a voltage threshold, for example. In response to sensing the signal, an impedance of impedance network  763  may be modulated to generate an authentication response signal. Modulating the impedance of receive charging coil  203  may be accomplished my opening and closing switch(es)  853 , for example. Wireless energy delivery is more efficient when the transmit charging coil and the receive charging coil are impedance matched. Thus, a higher amount of power is necessary to deliver wireless energy to the receive charging coil when the receive charging coil is impedance mismatched. Consequently, a higher amplifier current  731  provided to amplifier  745  may indicate an impedance mismatch (and less efficient wireless energy transfer) to the receive charging coil. A sagging amplifier voltage  732  may similarly indicate an impedance mismatch caused by the increase in amplifier current  731 . If a receiving device selectively matches and mismatches the impedance (e.g. using impedance network  763 ) of receive charging coil  203 , it can effectively communicate an authentication response signal that can be measured by the power that the amplifier  745  requires to send the authentication challenge signal within wireless energy  457 . 
     In process block  920 , wireless energy delivery from the transmit charging coil to a receive charging coil of the receiving device is initiated based at least in part on the at least one electrical attribute. 
     In one embodiment, when a rectified voltage (e.g.  766 ) is measured and transmitted back to the charger via the established wireless data channel, the charger verifies that the rectified voltage is within an expected range and subsequently initiates the wireless energy delivery. In one embodiment, when a series of electrical measurements of the amplifier voltage and/or current indicates a particular authentication response signal, the charger verifies the authentication response signal and subsequently initiates the wireless energy delivery. 
       FIG. 10  illustrates an example quadcopter  1002  having a receive charging coil  1003 , an example transmit charging coil  1005  included in a landing pad  1021 , and a charger  1011  coupled to drive the transmit charging coil  1005 , in accordance with an embodiment of the disclosure. Charger  1040  may include the components of charger  211  except that transmit charging coil  205  is replaced with a similar transmit charging coil  1005  included in landing pad  1021 . In the illustrated embodiment of  FIG. 10 , receive charging coil  1003  is coiled around, or integrated into, leg  1013  of quadcopter  1002 . In some embodiments, some or all or legs  1013  of quadcopter  1002  may include coils  1003  to facilitate charging of a battery  1095  that powers quadcopter  1002 . The components of device  301  (excluding battery  395  and receive charging coil  303 ) may also be included in quadcopter  1002  to facilitate charging of battery  1095 . It is appreciated by those skilled in the art that coils  1003  may be disposed somewhat remote from battery  1095  while still providing the energy via a wire to a wireless energy receiving module (e.g.  393 ) that converts and provides the wireless energy to battery  1095 . When a plurality of receive charge coils  1003  are utilized, they may be coupled to the same rectifier (e.g.  315 ) so that whichever receive charging coil(s)  1003  that are receiving the wireless energy can deliver the wireless energy to the rectifier. 
     In a land-based mobile robot system, wall-mountable enclosures that house a charger may be vertically mounted on walls for charging the land-based mobile robots. In an electric vehicle system, a floor-mounted enclosure may be utilized to house the charger (e.g.  211 ) and the receive charging coil may be mounted in the belly of the vehicle to recharge the electric vehicle&#39;s battery or batteries. 
     In contexts where devices that include batteries are deployed in cold temperatures, battery performance of those devices may suffer from the cold temperatures. In some embodiments, the wireless power transfer system of this disclosure may be utilized to generate heat to keep electronics and batteries warmer to increase performance in colder environments. 
     In one embodiment, load  776  of  FIG. 7  is located proximate to battery  395  and warming the battery  395  includes a charger providing wireless energy  457  to receive charging coil  203  and providing converted voltage  768  to load  776  to generate heat to heat battery  395 . In this embodiment, processing logic (e.g.  313 ) may keep switches  753 ( 1 ) and  753 ( 2 ) off while switch  753 ( 3 ) is turned on to provide converted voltage  768  to load  776  (e.g. resistor network spread around battery  395 ). 
     In one embodiment, one or more of impedance network  763 , rectifier  765 , or power converter  767  is located proximate to battery  395  and warming the battery  395  includes a charger providing wireless energy  457  to receive charging coil  203 . These components will generate heat due to receiving the wireless energy  457  and thus heat up battery  395 . 
     In one embodiment, impedance tuning of impedance network  763  is utilized to warm battery  395 . Generally, impedance network  763  may be tuned to facilitate efficiency and reduce heat loss due to impedance mismatch between transmit charging coil  205  and receive charging coil  203 . However, where heating the battery  395  is a goal, the impedance of impedance network  763  may be adjusted to be purposely inefficient to produce heat for battery  395 . By mismatching the impedance of receive charging coil  203 , more wireless energy  457  is reflected as reflected wireless energy  456  and heat generation on receive charging coil  203  is a byproduct of the mismatched impedance. Hence, where receive charging coil  203  is disposed proximate to battery  395  and where impedance network  763  is controlled (e.g. by processing logic  313 ) to create an impedance mismatch, receive charging coil  203  may beneficially generate heat for battery  395  from wireless energy  457 . In some embodiments, an impedance of impedance network  747  is adjusted to create an impedance mismatch between transmit charging coil  205  and receive charging coil  203  so that wireless energy  457  generates more heat on receive charging coil  203 . 
     In one embodiment, the magnitude of wireless energy  457  is increased so that the voltage generated on receive charging coil  203  is purposely higher than required to charge battery  395 . For example, if power converter  767  generates a converted voltage  768  of 12 VDC and is most efficient when rectified voltage is 14 VDC, the magnitude of wireless energy  457  may be increased such that rectified voltage  766  is 16 VDC so that power converter  767  generates more heat by stepping down a higher voltage (e.g. 16 VDC) to the 12 VDC for charging battery  395 . Increasing the magnitude of wireless energy  457  may include increasing the amplifier voltage  732  and/or increasing the gain of amplifier  745 . Increasing the magnitude of wireless energy  457  may also include increasing a duty cycle of transmitter signal  744 . 
     In one embodiment to warm battery  395 , the battery  395  is charged by turning switch  753 ( 1 ) on and subsequently battery  395  is discharged by coupling load  776  to battery  395  by closing switches  753 ( 3 ) and  753 ( 1 ). The charge/discharge functions can be cycled on and off to keep battery  395  warm. In one embodiment, warming the battery  395  includes increasing the battery current  771  by tuning the gate voltage  755 ( 1 ) so that the increased battery current  771  generates more heat/power from the electrical components between receive charging coil  203  and battery  395 . 
     In one embodiment, thermal sensor  799  (e.g. a thermistor) is disposed to provide a battery temperature of battery  395 . Processing logic  313  may periodically read thermal sensor  799  and when the thermal sensor  799  indicates that the battery temperature has reached a temperature threshold, processing logic  313  may send a message to a charger (e.g. charger  211 ) to provide heat to battery  395  using wireless energy  457 . Both the charger and/or the receiving device that includes the battery  395  may go into a battery warming mode to facilitate warming of battery  395  so that the battery temperature at thermal sensor  799  climbs over the temperature threshold. 
     Embodiments of the disclosure include systems that allow for and facilitate autonomous operation of a wireless power system. A charger such as wireless charger  211  may operate in a system idle mode when no recognizable devices are in range of charging. In the system idle mode, a microcontroller included in processing logic (e.g.  243 ) of the charger may be powered on, but the wireless power transmitter (e.g.  209 ) may be in a low power state where wireless energy  457  is not being delivered. In system idle mode, the charger may continue to periodically broadcast charging station data and transmit the data queries described in association with process block  605 . 
     The charger may enter a heartbeat mode when activity is detected by the charger. Activity may be detected based on a successful establishment of a wireless communication channel as discussed in operation  603 . The heartbeat mode may include authenticating one or more devices (e.g.  311 ) according to processes  600 . 
     Heartbeat mode may also include determining if a device is close enough to begin charging. To determine this, the device may measure the rectified voltage (e.g.  766 ) and report the rectified voltage to the charger over a wireless communication channel. If the rectified voltage is within a pre-determined range, wireless power transfer is continued by the charger. In one embodiment, the battery voltage (e.g.  772 ) of the device or amplifier current (e.g.  731 ) of the charger is used to determine if the device is close enough to begin charging. Using the amplifier current may be advantageous in that it does not require a wireless communication channel to be established between the charger and the device. The charger may also perform measurements to determine whether a device is within a suitable charging distance. For example, the charger may measure an amount of power consumed by amplifier  745 . If the power level is above a pre-determined value, the receive charging coil of the device may be too close to the transmit charging coil or there may be an interfering device present. 
     Furthermore, if a battery is already fully charged or severely discharged, charging the battery may cause damage to the battery and/or charger. Therefore, a device that measures electrical attributes of the battery (e.g.  772 ) and reports them back to the charger allows the charger to make informed decisions about whether to proceed to a power ramp-up mode of charging the battery. This information also allows the charger to intelligently decide which device to power, when two or more devices are present at a charger. Each device that is proximate to a charger may communicate task priorities such as time until a next task (e.g. a drone flight mission), which may allow the charger to prioritize charging of one of the devices. 
     The charger (e.g.  211 ) and device (e.g.  301 ) may receive and transmit a variety of information that can be stored in their memories. Data stored on the device may be queried by the charger over the wireless communication link. A device may download data or firmware updates via a wireless communication link provided by charger  211 , in some embodiments. Therefore, the charger can provide remote updates, security codes, flight plans, task instruction, and other data to the device while the device is charging or at least proximate to the charger. 
     Examples of data that the charger may record are: 1) number of connections with each device; 2) total amount of charging time for each receiver; 3) battery voltage when the device leaves the charger; 4) battery voltage when the device returns to the charger; 5) timestamps of when each device leaves the charger; 6) build configuration for the charger and the devices; 7) security authentication codes; 8) timestamp of when each device returns to the transmitter; 9) total amount of time the device is away from the charger; 10) voltage and current measurements to monitor power transfer; 11) error states of the charger and/or devices; and 12) preventative maintenance alerts. This data may be transferred from the charger to a network for cloud storage or cloud computing via WiFi or Ethernet, for example. The data may also be wirelessly communicated to the devices. 
     Examples of data that the device may record includes: 1) number of charge cycles for the device battery; 2) total energy delivered to the device battery; 3) time-stamped measurements of anomalies in the device battery; 4) total energy consumed by the device from the battery; 5) total energy delivered to the device battery; 6) the device battery state of charge; 7) battery lifetime cell charging/balancing statistics; 8) build configuration for the device; and 9) security authentication codes. This data may be wirelessly transferred from the device to the charger and ultimately to a network for cloud storage or cloud computing. 
     When the authentication of heartbeat mode is completed, the charge may proceed to a power ramp-up mode for devices that are within sufficient operating range of the charger and safety conditions have been met. In one embodiment, the wireless energy receiving module begins to ramp-up the amount of power it delivers to the device or battery of the device. Consequently, the charger increases the amount of power it delivers to the wireless energy receiving module. The wireless energy receiving module may have the ability to control the output voltage (e.g.  768 ) or current limit of the power delivered to the device. These two parameters can be pre-determined or updated dynamically over the wireless communication link between the charger and the device. The output voltage may be set once at the beginning of the ramp-up mode, but the current limits may be incrementally increased over a period of time. Increasing the current limit allows more current to flow to the device. As the current limit increases, the amount of power being provided by the charger must increase to maintain sufficient power delivery to the device. To do this effectively in real-time, the device may continuously monitor the rectified voltage that is sent back to the charger over the wireless communication channel. If the rectified voltage drops below a predetermined threshold, the charger will increase the amount of power it transmits wirelessly. If the rectified voltage exceeds a threshold, the charger may decrease the amount of power it transmits wirelessly. Other parameters can also be used for this determination, including but not limited to battery voltage, battery current, power amplifier voltage, power amplifier current, and reflected energy. Any of these parameters and/or measurements may be communicated via a wireless communication channel to provide a feedback loop. 
     After the battery current achieves a predetermined threshold, the power ramp-up mode may transition to a steadier battery charging mode having a constant current, which may be the maximum charge current for the battery. This predetermined current threshold may be maintained throughout the constant-current battery charging mode. The device may continuously monitor the state of the battery and may transition from constant-current to constant-voltage charging as the battery voltage approaches the float voltage (i.e. charge termination voltage) configured for the battery. If the power received by the device reduces (which could be caused by the device shifting around or temperature change of the charger causing it to reduce the amount of power it can deliver), the wireless energy receiving module can dynamically reduce the current delivered to the battery. This feedback loop may also ensure that the wireless energy receiving module will always have a supply of power greater than the power it provides to the battery or device. The charger may continue to monitor the power delivered and decrease the power as the charging power tapers off in constant-voltage charging mode. The receiver may alert the transmitter to terminate charging the battery when the current being drawn by the battery drops below 1/10 th  of the configured constant-current charging rate (the C/10 rate). To prevent over-charging the battery for the case where the devices is drawing more current from the battery than the C/10 rate, the wireless energy receiving module may pause charging after a configured time has elapsed (e.g. 1 to 3 hours), measure the battery voltage and terminate charging if the voltage is with the Recharge Threshold (or approximately 95%) of the float voltage configured for the battery. If the battery voltage is more than the Recharge Threshold below the float voltage, the end of a charge timer may be reset and charging may be resumed. Any of these fault detection or battery conditions can be communicated from the wireless energy receiving module to the device that will allow the device to make an independent decision or a decision can be recommended from the wireless energy receiving module based on that information. An example of such system could be a wireless energy receiving module detecting a battery depletion of an aerial drone. The system can alert the aerial drone to make a safe landing based on a battery fault detection. 
     The processes explained above are described in terms of computer software and hardware. The techniques described may constitute machine-executable instructions embodied within a tangible or non-transitory machine (e.g., computer) readable storage medium, that when executed by a machine will cause the machine to perform the operations described. Additionally, the processes may be embodied within hardware, such as an application specific integrated circuit (“ASIC”) or otherwise. 
     A tangible non-transitory machine-readable storage medium includes any mechanism that provides (i.e., stores) information in a form accessible by a machine (e.g., a computer, network device, personal digital assistant, manufacturing tool, any device with a set of one or more processors, etc.). For example, a machine-readable storage medium includes recordable/non-recordable media (e.g., read only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, etc.). 
     The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. 
     These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.