Abstract:
A wireless power transmission system includes a first power transmitter configured to transmit a first electromagnetic field, a first power receiver configured to generate electrical energy using the first transmitted electromagnetic field, a first occupancy sensor configured to indicate a first presence of a first individual within a first sensed area, and a control unit configured to control the first power transmitter based upon the indicated first presence.

Description:
This application claims the benefit of U.S. Provisional Application No. 61/839,618 filed Jun. 26, 2013, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to power transfer systems, and, more particularly, wireless charging systems. 
     BACKGROUND 
     Use of wireless sensors is rapidly increasing in residential, commercial, and industrial applications. For example, wireless sensors are used in alarm systems for residential and commercial buildings, for wireless temperature monitoring, and to detect occupancy in rooms. Buildings incorporating temperature and occupancy detection sensors, also known as “smart” buildings, can automatically control climate systems and lighting within the building. 
     Using wireless sensors for building applications enables simple retrofitting of buildings without the need for wiring electrical power to the sensors. However, wireless sensors are typically powered by a battery, which can power the sensor only for a limited duration. Replacing or recharging the batteries in wireless sensors can be cumbersome. One solution is to charge the wireless sensors remotely using electromagnetic energy, for example electromagnetic waves in the radio frequency band, also referred to as radio frequency (“RF”) charging. In an RF charging system, a power transmitter broadcasts energy, which is received by an antenna and converted into electric power to charge the batteries in the attached sensor. 
     Although RF power transmission is designed to satisfy safety regulations, some people perceive the RF electromagnetic radiation as hazardous to human health. What is needed, therefore, are improvements in RF power transmission that reduce the potential for exposure to RF electromagnetic radiation. 
     SUMMARY 
     In one embodiment, a wireless power transmission system includes a first power transmitter configured to transmit a first electromagnetic field, a first power receiver configured to generate electrical energy using the first transmitted electromagnetic field, a first occupancy sensor configured to indicate a first presence of a first individual within a first sensed area, and a control unit configured to control the first power transmitter based upon the indicated first presence. 
     In another embodiment, a method of operating a wireless power transmission system includes indicating a first presence of a first individual within a first sensed area using a first occupancy sensor, receiving the indication of the first presence of the first individual at a control unit, controlling with the control unit a first power transmitter based upon the received first indication, transmitting a first electromagnetic field with the first power transmitter under the control of the control unit, and generating electrical power from the first electromagnetic field with a first power receiver. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a building equipped with a wireless charging system having a control unit configured to selectively activate power transmitters. 
         FIG. 2  is a schematic diagram of another wireless charging system having a control unit connected to a web server. 
         FIG. 3  is a flow diagram of a process for selectively operating a wireless power transmitter. 
         FIG. 4  is a flow diagram of another process for selectively operating a wireless power transmitter. 
         FIG. 5  is a flow diagram of yet another process for selectively operating a wireless power transmitter. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the embodiments described herein, reference is now made to the drawings and descriptions in the following written specification. No limitation to the scope of the subject matter is intended by the references. This disclosure also includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the described embodiments as would normally occur to one skilled in the art to which this document pertains. 
       FIG. 1  depicts a schematic diagram of a place or asset such as a building, a residential house, a garage, a hotel, a factory, a hospital, a mall, or the like equipped with a wireless charging system  100 . In another embodiment, the asset can be a moving vessel such as a vehicle, a truck, a plane, a boat, a ship, or the like. The wireless charging system  100  includes a control unit  104 , at least one power transmitter, and at least one wireless device (e.g. sensor or actuator), each of which is operatively connected to an energy storage system/device/cell such as a battery. In the illustrated embodiment, the system  100  includes three power transmitters  108   a ,  108   b , and  108   c  and four sensors  112   a ,  112   b , and  112   c , which are connected to batteries  116   a ,  116   b , and  116   c , respectively. The power transmitters  108   a - 108   c  are each configured to generate an electromagnetic field  120 . In the illustrated embodiment, the power transmitters  108   a - 108   c  are radio-frequency (“RF”) antennas, though other power transmitters, such as inductive resonance loops or magnetic antennas, are used in other embodiments. 
     The sensors  112   a - 112   c  include occupancy sensors configured to detect whether a person occupies the room in which the sensors  112   a - 112   c  are mounted and to generate a corresponding signal. The signals generated by the occupancy sensors are delivered to the control unit  104  via a wireless signal transmitter, three wireless signal transmitters  114   a - 114   c  are illustrated, which transmit the signals via a known wireless signal transmission standard, for example Bluetooth, WiFi, Zigbee, TransferJet, UWB, NFC, EnOcean, dedicated short-range communication (DSRC), or RF signal transmission. In some embodiments, a wired connection or power line communication through wired receptacles is used to transmit the signals. The sensors  112   a - 112   c  each include a power receiver configured to receive electromagnetic radiation  120  generated by the power transmitters  108   a - 108   c  and convert the electromagnetic radiation  120  to electric power that charges the batteries  116   a - 116   c . In some embodiments, the sensors  112   a - 112   c  include additional sensors, for example temperature sensors, alarm sensors, thermal sensors, motion sensors, optical sensors, camera sensors, atmosphere sensors, and resistive sensors. In other embodiments, the sensors  112   a - 112   c  are connected directly to a building power source via, for example, a wired receptacle, while the wireless power transmitters  108   a - 108   c  are configured to deliver power to charge batteries connected to other sensors and electronic components in the building. In other embodiments, more than one sensor is connected to a shared power receiver to receive electromagnetic radiation generated by one or more power transmitters  108   a - 108   c . In further embodiments, the sensors, power receivers, power transmitters, or any combination thereof can be mounted, embedded, or integrated in any asset structures such as a ceiling, a wall, a window, a door, a floor, a roof, or the like. 
     The control unit  104  is operatively connected to a power source  124  to receive electric power from the power source  124 . In the illustrated embodiment, the power source  124  is AC power wired to the building in which the wireless charging system  100  is installed. In other embodiments, the power source is a battery, a generator, a solar receiver, or any other suitable source of electric power. The power source can be mounted, embedded, or integrated in any asset structures such as a ceiling, a wall, a window, a door, a floor, a roof, or the like. The control unit  104  includes a controller  128 , a memory unit  132 , a timer  136 , and an optional web server  140 . The control unit  104  is operatively connected to the power transmitters  108   a - 108   c  to enable the control unit  104  to selectively activate the power transmitters  108   a - 108   c.    
     The control unit  104  is operatively connected to a switch  144  to enable a user to manually activate and deactivate the power transmitters  108   a - 108   c . In some embodiments, the switch  144  is positioned on one of the power transmitters  108   a - 108   c  or a separate switch is positioned on each power transmitter  108   a - 108   c , while in other embodiments the switch  144  or switches are remote from the power transmitters  108   a - 108   c . In different embodiments, the wireless charging system  100  includes a remote control  148  that enables a user to selectively activate any or all of the power transmitters  108   a - 108   c  or change operating parameters of the wireless charging system  100 . In various embodiments, the control unit  104  is operatively connected to a building control system  152 , which operates, for example, lighting, climate control, and an alarm system in the building. In other embodiments, the control unit  104  is integrated with the building control system  152 . In further embodiments, the control unit  104  is integrated into the power transmitter. 
     Operation and control of the various components and functions of the wireless charging system  100  are performed with the aid of the controller  128 . The controller  128  is implemented with general or specialized programmable processors that execute programmed instructions. The instructions and data required to perform the programmed functions are stored in the memory unit  132  associated with the control unit  104 . The processors, the memory  132 , and interface circuitry configure the controller  128  to perform the functions described above and the processes described below. These components can be provided on a printed circuit card or provided as a circuit in an application specific integrated circuit (ASIC). Each of the circuits can be implemented with a separate processor or multiple circuits can be implemented on the same processor. Alternatively, the circuits can be implemented with discrete components or circuits provided in VLSI circuits. Also, the circuits described herein can be implemented with a combination of processors, ASICs, discrete components, or VLSI circuits. 
     In operation, the control unit  104  is configured to selectively activate any or all of the power transmitters  108   a - 108   c  to generate the electromagnetic field  120 . The sensors  112   a - 112   c  each have a power receiving antenna that absorbs the electromagnetic energy  120  and converts the energy into electric power, which is used to charge the batteries  116   a - 116   c  connected to the sensors  112   a - 112   c , respectively. In another embodiment, the sensors are configured to connect to a shared power receiving antenna. 
     The timer  136  is configured to recall a program stored in memory  128  such that the control unit  104  activates any or all of the power transmitters  108   a - 108   c  only at predetermined times. The timer  136  is programmed by the remote control  148 , by manual input, or by a computer or smartphone connected to the timer  136  via the web server  140 . To minimize exposure to the electromagnetic radiation, the timer  136  is preferably set such that the control unit  104  activates the power transmitters  108   a - 108   c  only when the room in which they are located is typically unoccupied, for example at night in offices or during work hours in a residence. 
     The web server  140  connects the control unit  104  to an electronic device such as a computer, a smartphone, a tablet, a gaming console, a laptop, or the like via internet protocol (“IP”). In some embodiments, the web server  140  is a local server, connected only to a local area network, while in other embodiments the web server is connected to the internet, enabling the control unit  104  to be programmed and controlled remotely from any internet-connected computer or smartphone. The web server can also be in a remote place and control the power transmitters via a connection, for example an IP connection. 
     The memory  132  of the control unit  104  stores the programming instructions for the timer  136  and for the controller  128 . Additionally, the control unit  104  generates a log, which is stored in the memory  132 , to record the times when each of the power transmitters  108   a - 108   c  are active. A user can then access the log via the web server  140  to monitor the human exposure to the electromagnetic radiation. 
     In the illustrated embodiment, the wireless charging system  100  includes three power transmitters  108   a - 108   c . Wireless power transmitter  108   a  is configured to transmit power to two wireless sensors  112   a , located in different rooms of the building when the rooms are unoccupied. Wireless power transmitters  108   b  and  108   c  generate a lower strength electromagnetic field  120 , and are configured to transmit power only within a single room to sensors  112   b  and  112   c , respectively, when the associated occupancy sensor detects that the room in which it is located is unoccupied. In some embodiments, the wireless charging system includes a single wireless power transmitter, which generates an electromagnetic field strong enough to be received by all sensors throughout the building. In such a system, the control unit can be configured to activate the wireless power transmitter only when the sensors indicate that the entire building is unoccupied or nearly unoccupied. 
       FIG. 2  is a schematic illustration of another embodiment of a wireless charging system  200 . The wireless charging system  200  includes a power transmission system  204 , a receiving system  208 , and an occupancy sensor system  212 , which, in the illustrated embodiment, are all located in a single room  202 . 
     The power transmission system  204  includes a control unit  216  and a power transmitter  220 , both of which are operatively connected to a power source  224 . The control unit  216  is configured to selectively activate the power transmitter  220  to emit electromagnetic energy  228  into the room  202 , directed towards the receiving system  208  and the occupancy sensor system  212 . 
     The receiving system  208  includes a power receiver  232 , at least one sensor, for example an alarm sensor  236  and a temperature sensor  240 , emergency lighting  244 , and an energy storage system/device/cell such as a battery  248 . The power receiver is configured to receive the electromagnetic energy  228  generated by the power transmitter  220  and convert the received energy into electric power to charge the battery  248 . The battery  248  is operatively connected to the sensors  236  and  240  and the lighting  244  to enable the sensors  236  and  240  and the lighting  244  to operate with the energy stored in the battery  248 . 
     The occupancy sensor system  212  includes an optional power receiver  252 , an occupancy sensor  256 , and a battery  260 . In alternate embodiments, the occupancy sensor system is powered by a wired connection to a power supply. The power receiver  252  receives the electromagnetic energy  228  generated by the power transmitter  220  and converts the received energy to electrical energy to charge the battery  260 , which powers the occupancy sensor  256 . The occupancy sensor  256  is configured to detect the presence of a person in the room  202 , and to generate a corresponding signal, which is delivered to the control unit  216 . In some embodiments, the power receiver  252  is configured to transmit the sensor signal to the power transmitter, while in other embodiments other known wired or wireless signal transmission systems are used to transmit the sensor signal to the control unit. 
     The control unit  216  is optionally connected to a web server  264 , which is remote of the power transmission system  204 . The web server  264  is configured to be controlled by an electronic device such as a smartphone  268 , a computer  272 , a tablet, a gaming console, a laptop, or the like to enable a user to remotely select operating parameters for activating the power transmitter  224  and to manually activate or deactivate the transmitter  224 . In some embodiments, the web server  264  operates a plurality of wireless charging systems, each located in a different room of an asset such as a building or building complex. Each wireless charging system can be programmed to operate independently of the others. 
     In other embodiments the web server can be implemented on the power transmission system  204 . 
     In some embodiments, the control unit  216  is configured to selectively activate the wireless power transmitter  220  based on the sensor signals received from the occupancy sensor  212 . If the sensor signal indicates that the room  202  is unoccupied, the control unit  216  activates the power transmitter  220  to generate electromagnetic energy  228 , which is received by the power receivers  232  and  252  to charge the batteries  248  and  256 , respectively. If the control unit  216  receives a sensor signal indicating that the room  202  is occupied, the control unit  216  deactivates the power transmitter  220 , thereby minimizing exposure of occupants of the room  202  to the electromagnetic energy  228 . 
       FIG. 3  illustrates a process  300  for operating a wireless charging system, such as the wireless charging systems of  FIG. 1  and  FIG. 2 . The process  300  refers to a controller, such as the controller  128  and the control unit  216  described above, executing programmed instructions stored in a memory, for example memory  132 , operatively connected to the controller to cause the controller to operate one or more components of the system to perform the specified function or action described in the process. 
     The process begins with the controller receiving an occupancy signal from an occupancy sensor (block  310 ). In some embodiments, the occupancy signal is localized to an individual room or area of a building, while in other embodiments the occupancy signal is indicative of occupancy in any portion of the building in which the system is installed. The controller then determines if occupancy is detected in the room or building (block  320 ). If the asset, such as the room or building, is occupied, the wireless power transmitter is deactivated (block  330 ), thereby minimizing exposure of occupants to electromagnetic radiation, and the process continues from block  310 . If the room or building is unoccupied, the controller activates the wireless power transmitter (block  340 ) to enable the batteries of the occupancy sensors and other wireless electronic devices to charge without risking occupant exposure to electromagnetic radiation. In some embodiments, the controller is further configured to record when the power transmitter is active (block  350 ) in a log that is stored in a memory, to enable a user to recall the times during which the power transmitter is active. The process then continues from block  310 . 
       FIG. 4  illustrates another process  400  for operating a wireless charging system. The process  400  refers to a controller, such as the controller  128  and the control unit  216  described above, executing programmed instructions stored in a memory, for example memory  132 , operatively connected to the controller to cause the controller to operate one or more components of the system to perform the specified function or action described in the process. 
     The process  400  begins with the controller receiving a signal indicating a level of charge in a battery that operates a sensor or other electronic component (block  410 ). The controller determines whether the level of charge is below a threshold value, indicating that the battery has a low charge (block  420 ). If the charge is above the threshold value, the power transmitter is deactivated (block  430 ) and the process continues with block  410 . If the charge is below the threshold value, the power transmitter is activated to enable the battery to be charged (block  440 ), and the process repeats from block  410 . The power transmitter therefore emits electromagnetic radiation only when the batteries in the system are in need of charging, thus reducing the amount of time the power transmitter is active, and lowering the occupant exposure accordingly. 
       FIG. 5  illustrates another process  500  for operating a wireless charging system, such as the wireless charging systems of  FIG. 1  and  FIG. 2 . The process  500  refers to a controller, such as the controller  128  and the control unit  216  described above, executing programmed instructions stored in a memory, for example memory  132 , operatively connected to the controller to cause the controller to operate one or more components of the system to perform the specified function or action described in the process. 
     The process  500  begins with the controller receiving an occupancy signal from an occupancy sensor located in an asset, which may be for example, a room or a building (block  510 ). The controller then determines if occupancy is detected in the asset (block  520 ). If the asset is occupied, the wireless power transmitter is deactivated (block  530 ), thereby minimizing exposure of occupants to electromagnetic radiation, and the process continues from block  510 . If the room or building is unoccupied, the controller then receives a signal indicating a level of charge in a battery that operates a sensor or other electronic component (block  540 ). The controller determines whether the level of charge is below a threshold value, indicating that the battery has a low charge (block  550 ). In one embodiment, the threshold value is approximately 98% of the full charge of the battery, though other threshold values are used in alternate embodiments. If the charge is above the threshold value, the power transmitter is deactivated (block  530 ) to reduce power consumption by the power transmitter, and the process continues with block  510 . If the charge is below the threshold value, the power transmitter is activated to enable the battery to be charged (block  560 ) without risking occupant exposure to electromagnetic radiation. The controller is further configured to record when the power transmitter is active (block  570 ) in a log that is stored in a memory, to enable a user to recall the times during which the power transmitter is active. The process then continues from block  510 . 
     The power transmitter therefore emits electromagnetic radiation only when the area in which the power transmitter is installed is unoccupied and the batteries in the system are in need of charging. Occupant exposure is reduced since the power transmitter is active when the area of the power transmitter is unoccupied. Furthermore, the cost of operation is reduced since the power transmitter is not active when the batteries are fully or nearly fully charged. 
     It will be appreciated that variants of the above-described and other features and functions, or alternatives thereof, may be desirably combined into many other different systems, applications or methods. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements may be subsequently made by those skilled in the art that are also intended to be encompassed by the foregoing disclosure.