Abstract:
A system for transmission of data and electrical power comprising: a plurality of independent power sources, each one of the plurality of independent power sources being connected to a respective one of a plurality of electrical power lines; and a modulator configured to modulate a carrier signal with a data signal received at an input of the modulator so as to generate a modulated carrier signal at an output thereof, wherein the output of the modulator is coupled to each of the plurality of electrical power lines, to permit transmission of the modulated carrier signal over the plurality of electrical power lines, such that the plurality of electrical power lines form a data network while maintaining electrical isolation between each of the plurality of electrical power lines.

Description:
FIELD OF THE INVENTION 
     The present application relates to a system for transmission of data and power. In particular, the invention relates to a system in which data signals are transmitted over electrical power transmission lines. 
     BACKGROUND TO THE INVENTION 
     Many industrial and vehicular systems require both power and data to be provided to a sensor or actuator. For example, systems have been proposed in which a plurality of sensors and actuators are provided in individual zones of a control system. 
     In the proposed systems, each individual actuator requires its own power supply, whilst individual zone of the control system is provided with a plurality of sensors which provide data to a central data network of a host system. The central data network, which is typically a conventional data network, in turn provides control signals to the individual actuators, to control their operation. 
     The data signals transmitted by the sensors to the central data network and from the central data network to the individual actuators are carried by dedicated wired data connections. It will be appreciated that in control systems within large structures such as an aircraft wing, a significant amount of electrical cable is required for the wired data connections, which adds to the weight and cost of the structure. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention, there is provided a system for transmission of data and electrical power comprising: a plurality of independent power sources, each one of the plurality of independent power sources being connected to a respective one of a plurality of electrical power lines; and a modulator configured to modulate a carrier signal with a data signal received at an input of the modulator so as to generate a modulated carrier signal at an output thereof, wherein the output of the modulator is coupled to each of the plurality of electrical power lines, to permit transmission of the modulated carrier signal over the plurality of electrical power lines, such that the plurality of electrical power lines form a data network whilst maintaining electrical isolation between each of the plurality of electrical power lines. 
     The system of the present invention permits transmission of data over electrical power lines, and thereby obviates the need for dedicated data cabling in systems where an electrical power connection is present. This in turn leads to a reduction in the cost and weight associated with providing dedicated data cabling. 
     The system may further comprise a demodulator having an input coupled to each of the plurality of electrical power lines, to permit recovery of a data signal transmitted in a modulated carrier signal received over one of the plurality of electrical power lines from a remote data node. 
     Thus, the system permits bidirectional data communication over the electrical power lines. 
     The output of the modulator may be electromagnetically coupled to the plurality of power lines. 
     Alternatively, the output of the modulator may be capacitively coupled to the plurality of power lines. 
     The modulator may be configured to modulate a plurality of carrier signals with the data signal received at the input thereof. 
     For example, the modulator may be configured to modulate the plurality of carrier signals using an orthogonal frequency division multiplexing (OFDM) modulation scheme. 
     The data received at the input of the modulator may comprise Internet Protocol (IP) data packets. 
     The system may further comprise a further modulator configured to modulate a carrier signal with a data signal received at an input of the modulator so as to generate a modulated carrier signal at an output thereof. 
     This further modulator provides redundancy, to ensure that failure of the modulator does not cause failure of the entire system, as the further modulator can be brought online in the event of failure of the modulator. 
     The system may further comprise a remote data node coupled to one of the plurality of power lines, the remote data node having a demodulator configured to receive the modulated carrier signal and demodulate the modulated carrier signal to recover the data signal. 
     The remote data node may be powered by the one of the plurality of power lines. 
     Alternatively, the remote data node may be powered by an external power source. 
     The external power source may comprise a battery or capacitor which is charged by an energy harvesting device, for example. 
     According to a second aspect of the invention, there is provided a remote data node for use in the system of the first aspect, the remote data node comprising a demodulator configured to receive the modulated carrier signal and demodulate the modulated carrier signal to recover the data signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described, strictly by way of example only, with reference to the accompanying drawings, of which: 
         FIG. 1  is a schematic representation of an exemplary system for transmission of data and power; 
         FIG. 2  is a schematic representation of a remote data node for use in the system shown in  FIG. 1 ; 
         FIG. 3  is a schematic representation of an alternative embodiment of a remote data node for use in the system shown in  FIG. 1 ; 
         FIG. 4  is a schematic representation of an embodiment of a data distribution node suitable for use in the system shown in  FIG. 1 ; and 
         FIG. 5  is a schematic representation of a exemplary system for transmission of data and power over multiple power lines, in which multiple remote data nodes are coupled to individual power lines. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Referring first to  FIG. 1 , an exemplary system for transmission of data and electrical power is shown generally at  10 . The system  10  comprises a plurality of independent power sources  12 , from which electrical power is distributed to independent loads  14  via power lines  16 . In the example illustrated in  FIG. 1 , there are two power sources  12 , two loads  14  and two power lines  16 , but it is to be understood that the system  10  may include more than two power sources, loads and power lines. The loads  14  may be, for example, electro-thermal heating elements, where the system  10  is used as part of an aircraft wing ice protection system. 
     Coupled to the power lines  16  are remote data nodes  20   a ,  20   b . The remote data nodes  20   a ,  20   b  receive data from sensors  22  and/or actuators  24  that are external to the remote data nodes  20   a ,  20   b , and may also transmit data to the sensors  22  and/or actuators  24 . Where the system  10  is used as part of an aircraft wing ice protection system, the sensors may include temperature sensors, for example. 
     Data transmitted by the sensors  22  and actuators  24  to the remote data nodes  20   a ,  20   b  is transmitted by the remote data nodes  20   a ,  20   b  to a central data network  30 , which may be a generally conventional data network, using the power lines  16  as a transmission medium. Similarly, data can be transmitted from the central data network  30  to the remote data nodes  20   a ,  20   b  using the power lines  16  as a transmission medium. The central data network  30  may be, for example, an avionics data bus of an aircraft, where the system is used as part of an aircraft wing ice protection system or other aircraft sub-system. 
     To enable the transmission of data to and from the remote data nodes  20   a ,  20   b  using the power lines  16  as the transmission medium, the system  10  includes a data distribution node  40 . The data distribution node  40  is configured to receive data from the data network  30  and to modulate the received data for transmission over the power lines  16 . The data distribution node  40  is also configured to receive data from the remote data nodes  20   a ,  20   b  via the power lines  16  and demodulate the received data for onward transmission to the central data network. 
     To this end, the data distribution node  40  includes a gateway  42 , which acts as an interface between the central data network  30  and the system  10 . The gateway  42  is operative to receive digital data from the central data network  30  and to pass the received data to a modem (MOdulator/DEModulator)  44  of the data distribution node  40 . This will be referred to as data transmission in a forward direction. The gateway  42  is also operative to receive data from the modem  44  and to pass the received data to the central data network  30 . This will be referred to as data transmission in a reverse direction. Thus, the gateway  42  communicates bi-directionally with the central data network  30 . 
     In the forward direction, the modem  44  receives digital data from the gateway  42  and modulates it onto a carrier signal, to permit transmission of the modulated data over the transmission lines  16 . In one embodiment, the modem  44  modulates the digital data using an orthogonal frequency division multiplexing (OFDM) scheme, in which the digital data is modulated onto multiple different carrier frequencies. OFDM is a particularly suitable modulation scheme for modulating the digital data for transmission over the power lines  16 , due to its ability to cope with the channel conditions present in the power lines, such as high frequency attenuation. However, it is to be understood that other modulation schemes may be used. 
     In the reverse direction, the modem  44  receives one or more modulated carriers carrying digital data transmitted from the remote data nodes  20   a ,  20   b , and demodulates the carriers to recover the digital data, so that it can be transmitted, via the gateway  42 , to the central data network  30 . Again, in one embodiment, the digital data transmitted by the remote data nodes  20   a ,  20   b  is modulated onto multiple carrier waves using an OFDM modulation scheme, although it is to be understood that other modulation schemes may also be used. 
     To enable the modulated carrier signals from the modem  44  to be transmitted to the remote data nodes  20   a ,  20   b  using the power lines  16 , and to enable modulated carrier signals from the remote data nodes  20   a ,  20   b  to be passed on to the modem  44 , the data distribution node  40  includes bi-directional couplers  46 , which couple the data distribution node  40 , and more specifically the modem  44 , to the power lines  16 . 
     The couplers  46  couple the modem  44  to the power lines  16  without any direct electrical connection. For example, the couplers  46  may use electromagnetic or transformer coupling to place modulated carrier signals on the power lines  16 , and to retrieve modulated carrier signals from the power lines  16 . Alternatively, the couplers  46  may use capacitive coupling to place the modulated carrier signals on the power lines  16 . In either case, this coupling creates a ubiquitous data network, comprising the power lines  16 , central data network  30 , remote data nodes  20   a ,  20   b , sensors  22  and actuators  24  whilst maintaining electrical isolation between the power lines  16 . 
     A bus guardian  48  is provided between each of the couplers  46  and the modem  44 . The bus guardians  48  provide supervisory functions for each channel of the data distribution node  40  and the related remote data node  20   a ,  20   b . In the event of a fault, either at the remote data node  20   a ,  20   b  or at the relevant channel of the data distribution hub  40 , the relevant bus guardian  48  can operate to isolate the remote data node  20   a ,  20   b  that is served by that bus guardian  48  from the data distribution node  40 , if the fault is of sufficient severity and/or persistence. 
     The data distribution node  40  is powered by a power supply module  50 , which receives electrical power from an external power supply to supply electrical power to the data distribution node  40 . 
     As can be seen from  FIG. 1 , the system  10  also includes filter/attenuators  60 , which are connected in series with the power lines  16 . In the example illustrated in  FIG. 1 , the filter/attenuators  60  are positioned within the data distribution node  40 , but it will be appreciated that the filter/attenuators  60  may be positioned elsewhere on the power lines  16  or within the system  10 , or may be omitted if not required. For example, the remote data nodes  20   a ,  20   b  may be provided with filter/attenuators  60  if required. 
     The filter/attenuators  60  are operative to attenuate the modulated carrier signals superimposed on the power lines  16 , to the extent required by relevant standards. The filter/attenuators  60  may also operate as bi-directional filters, to filter noise from the power sources  12 , and to prevent leakage of the modulated carrier signals upstream to the power source  12  and downstream to the loads  14 . 
     The structure and operation of the remote data nodes  20   a ,  20   b  will now be discussed in detail with reference to  FIGS. 2 and 3  of the drawings. 
     As can be seen from  FIG. 2 , in one embodiment a remote data node  20   a  draws its electrical power from the power line  16  to which it is coupled. In this embodiment, the remote data node  20   a  includes a power supply module  70 , which is operative to draw electrical power from the power line  16  and transform the electrical power into a form usable by the remote data node  20   a . For example, the electrical power line may carry high voltage direct current (HVDC) electricity to power a load  14 , whereas the remote data node may require a lower voltage DC power supply. Thus, the power supply module  70  may include a DC-DC converter or other transformer arrangement to supply electrical power to the remote data node  20   a  in a usable form. 
     The remote data node  20   a  includes a modem  72 , which is bi-directionally coupled to a host  74 . The host  74  is in turn bi-directionally coupled to the sensors  22  and/or actuators  24 . For example, where the system  10  is used as part of an aircraft wing ice protection system, the host  64  may be coupled both to sensors  22 , in the form of temperature sensors, and to actuators  24 , in the form of electrically operated switches. such as insulated gate bipolar transistors (IGBTs) or metal-oxide semiconductor field effect transistors (MOSFETs), which control electro-thermal heating elements on a wing of the aircraft. 
     In the forward direction, the modem  72  receives one or more modulated carrier signals transmitted via the power line  16 , and demodulates the carriers to recover the digital data, which may be, for example, control or command data for the actuators  24 . The modem  72  transmits the demodulated data to the host  74 , which in turn passes on the demodulated data to the actuators  24 . 
     In the reverse direction, the modem  72  receives digital data such as sensor data from the host  74 , and modulates the received digital data onto a carrier signal, to permit transmission of the modulated data over the transmission lines  16 . In one embodiment, the modem  72  modulates the digital data using an orthogonal frequency division multiplexing (OFDM) scheme, but it is to be understood that other modulation schemes may be used. 
     The host  74  acts as an interface between the modem  72  and the sensors/actuators  22 / 24 , implementing application and communications functionality to facilitate transmission of control data from the modem  72  to the actuators  24 , and transmission of sensor data from the sensors  22  to the modem  72 . 
     The remote data node  20   a  also includes a bi-directional coupler  76 , which couples the remote data node  20   a  to the power line  16 . The coupler  76  couples the modem  72  to the power line  16  without any direct electrical connection. For example, the coupler  76  may use electromagnetic or transformer coupling to place modulated carrier signals on the power line  16 , and to retrieve modulated carrier signals from the power lines  16 . This coupling of the remote data node  20   a , together with the coupling between the modem  42  of the data distribution node  40  and the other power lines  16  within the system  10 , creates a ubiquitous data network, comprising the power lines  16 , central data network  30  and remote data nodes  20   a , whilst maintaining electrical isolation between the power lines  16 . 
     The remote data node  20   a  also includes a bus guardian  78 , which performs a function similar to the bus guardians  48  of the data distribution node  40 , providing supervisory functions for the remote data node  20   a , such that in the event of a fault of sufficient severity and/or persistence at the remote data node  20   a , the remote data node  20   a  can be isolated from the data distribution node  40 . 
     In an alternative embodiment, illustrated in  FIG. 3 , a remote data node  20   b  does not draw electrical power from the power line  16 , but instead receives power from an external power supply. 
     The structure and operation of the remote data node  20   b  are very similar to those of the remote data node  20   a , and so in  FIG. 3 , like reference numerals denote elements that are common to both the remote data node  20   a  and the remote data node  20   b . For the sake of clarity and brevity, those common elements will not be described in detail here. 
     The remote data node  20   b  differs from the remote data node  20   a  in that the remote data node  20   b  draws its electrical power from a dedicated external power supply  80 , rather than from the power line  16 . The dedicated external power supply  80  may be, for example, one or more batteries, and/or one or more capacitors or supercapacitors. The batteries and/or capacitors/supercapacitors may store electricity generated by energy harvesting devices that convert, for example, kinetic energy into electricity. 
     The remote data node  20   b  also differs from the remote data note  20   a  in that it includes a gateway  82 , which acts as an interface between a modem  72  of the remote data node  20   b  and a private data network  84 . The private data network  84  may be, for example, a private data network used by sensors and actuators of the system  10  to transmit command and sensor data. Thus, the remote data node  20   b  is not necessarily directly connected to any sensors or attenuators, but may instead transmit and receive command and sensor data via the private data network  84  to sensors and/or actuators. 
     As in the remote data node  20   a  described above, in the forward direction, the modem  72  receives one or more modulated carrier signals transmitted via the power line  16 , and demodulates the carriers to recover the digital data, which may be, for example, command data. The modem  72  transmits the demodulated data to the gateway  82 , which in turn passes on the demodulated data. 
     In the reverse direction, the modem  72  receives digital data such as sensor data from the gateway  82 , and modulates the received digital data onto a carrier signal, to permit transmission of the modulated data over the transmission lines  16 . In one embodiment, the modem  72  modulates the digital data using an orthogonal frequency division multiplexing (OFDM) scheme, but it is to be understood that other modulation schemes may be used. 
     It will be appreciated that the two different types of remote data node  20   a  and  20   b  are interoperable, that is to say that the system  10  may include both remote data nodes  20   a  and remote data nodes  20   b . Equally, the system  10  may include exclusively one type of remote data node  20   a ,  20   b . Furthermore, the system  10  may include multiple remote data nodes  20   a ,  20   b  associated with one or each of the power lines  16 . 
     In some embodiments, the central data network  30 , remote data nodes  20   a ,  20   b  and private data network  84  operate under the conventional Internet Protocol (IP) to transmit packets of data from one element of the system  10  to another element of the system  10 . The use of IP enables data packets to be addressed to the relevant element of the system  10  without requiring complex switching or multiplexing. However, it will be appreciated that any suitable communications protocol could equally be employed. For example, the central data network  30 , remote data nodes  20   a ,  20   b  and private data network  84  may operate under a CAN (controller area network), TTP (time triggered protocol) or other suitable networking protocol. 
     For example, a command may be generated at the central data network  30  to cause a selected one of the actuators  24  to operate. The command is transmitted as one or more IP data packets, each of which is addressed to the selected one of the actuators  24 . The packets are transmitted by the gateway  42  to the modem  44 , which modulates them onto one or more carriers for onward transmission, as described above. The modulated carriers are transmitted in parallel to all of the bi-directional couplers  46  illustrated in  FIG. 1 , such that the data packets are transmitted, via the power lines  16 , to all of the remote data nodes  20   a ,  20   b . At the remote data nodes  20   a ,  20   b , the modulated carriers are demodulated by the modems  72  to recover the data packets representing the command. The data packets are decoded by the host  74  in the remote data node  20   a  to determine their destination, and are passed on to the appropriate sensors  22  and/or actuators  24 . In the remote data node  20   b , the data packets are passed on by the gateway  82  to the private data network  84 . The actuator  24  to which the packets are addressed (i.e. the actuator  24  having an address that corresponds to the address in the address field of the data packets) carries out the command. All other elements of the system simply ignore the command, since the data packets representing the command are not addressed to them. 
     Thus, the use of an Internet Protocol based data network facilitates the transmission of data between elements of the system  10  without requiring complex switching or multiplexing arrangements. Instead, IP data packets are effectively broadcast to all elements of the system  10 , and are acted upon only by those elements to which the data packets are addressed. 
       FIG. 4  is a schematic representation of an alternative embodiment of a data distribution node  100 . The data distribution node  100  includes many of the elements of the data distribution node  40  described above and illustrated in  FIG. 1 , and so like reference numerals have been used to designate like elements. For the sake of clarity and brevity those common elements will not be described in detail here. 
     The data distribution node  100  illustrated in  FIG. 4  differs from the data distribution node  40  illustrated in  FIG. 1  in that it includes duplicate gateways  42   a ,  42   b , duplicate modems  44   a ,  44   b  and duplicate power supply modules  50   a ,  50   b . The gateways  42   a ,  42   b  of the data distribution node  100  operate in the same manner as the gateway  42  of the data distribution node  40 , receiving data from the central data network  30  and pass it on to the modems  44   a ,  44   b . Similarly, the modems  44   a ,  44   b  of the data distribution node  100  operate in the same manner as the modem  44  of the data distribution node  40 . The power supply modules  50   a ,  50   b , each receive electrical power from an external power supply to power a respective pair of duplicate gateways  42   a ,  42   b  and modems  44   a ,  44   b.    
     The duplicate gateways  42   a ,  42   b , modems  44   a ,  44   b  and power supply modules  50   a ,  50   b  are provided for the purpose of redundancy, such that in the event of the failure of one of the gateways  42   a ,  42   b , modems  44   a ,  44   b  or power supply modules  50   a ,  50   b , the relevant duplicate gateway  42   b ,  42   a , modem  44   b ,  44   a  or power supply module  50   b ,  50   a  can be activated, to ensure that there is minimal loss of functionality. 
     To manage the operation of the duplicate gateways  42   a ,  42   b  modems  44   a ,  44   b  and power supply modules  50   a ,  50   b , the data distribution node  100  is provided with a redundancy management unit  102 . The redundancy management unit  102  is configured to monitor the duplicate modems  44   a ,  44   b  and gateways  42   a ,  42   b  and to disable an active modem  44   a  and its associated gateway  42   b  in the event of a fault or loss of power of sufficient severity or persistence. The redundancy management unit  102  simultaneously enables the duplicate modem  44   b  and its associated gateway  42   a . In this way, failure of a single modem  44   a ,  44   b , gateway  42   a ,  42   b  or power supply module  50   a ,  50   b  does not compromise the operation of the entire system  10 . 
     Although  FIG. 1  illustrates a system  10  in which a single remote data node  20   a ,  20   b  is coupled to each of the two power lines  16 , it will be appreciated that multiple remote data nodes  20   a ,  20   b  may be coupled to a single power line  16 , and that any combination of remote data nodes  20   a ,  20   b  may be coupled to a power line  16 . This is illustrated schematically in  FIG. 5 . 
     In  FIG. 5 , an exemplary system for transmission of data and electrical power is shown generally at  200 . The system  200  includes many of the elements of the system  10  described above and illustrated in  FIG. 1 , and so like reference numerals have been used to designate like elements. For the sake of clarity and brevity those common elements will not be described in detail here. 
     The system  200  comprises a dual redundant data distribution node  100  of the type described above and illustrated in  FIG. 4 , which is operative to couple data signals to, and decouple data signals from, a plurality (in this example 4) of power lines  16   a ,  16   b ,  16   c ,  16   d.    
     As can be seen in  FIG. 5 , two remote data nodes  20   a  of the type described above and illustrated in  FIG. 2 , are coupled to a first power line  16   a , whilst a single remote data node  20   a  of the type described above and illustrated in  FIG. 2  is coupled to a second power line  16   b . A single remote data node  20   b  of the type described above and illustrated in  FIG. 3  is coupled to a third power line  16   c . A further two remote data nodes  20   a  of the type described above and illustrated in  FIG. 2  and a further single remote data node  20   b  of the type described above and illustrated in  FIG. 3  are coupled to a fourth power line  16   d.    
     Thus, the system  200  of  FIG. 5  supports multiple power lines, with multiple remote data nodes on a single power line, and also supports a mixture of different types of remote data nodes on a single power line. 
     As will be appreciated from the foregoing, the system  10  described herein provides a flexible and reliable way for transmitting data over an electrical power network, and can be used to reduce the cost and weight associated with data cabling in systems where both data and power connections are required. 
     Although the system  10  has been described in the exemplary context of an aircraft wing ice protection system, it will be apparent to those skilled in the relevant arts that the principles of the system  10  are equally applicable to a great many applications and transportation platforms. 
     Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.