Power aware techniques for energy harvesting remote sensor system

A distributed monitoring system for monitoring one or more operating conditions of a structure includes: one or more sensor nodes coupled to the structure, each sensor node including: a power supply adapted to scavenge energy directed at the power supply; a sensor operably coupled to the power supply for sensing one or more operating conditions of the structure in the environment; and a communications interface operably coupled to the power supply and the sensor for communicating the sensed operating conditions of the structure; a communication network operably coupled to the sensor nodes; one or more controllers operably coupled to the communication network for monitoring the sensor nodes; and an energy radiator positioned proximate the structure adapted to radiate energy at the power supplies of the sensor nodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to patent application Ser. No. 12/208,222, filed on Sep. 10, 2008, the disclosure of which is incorporated by reference.

BACKGROUND

This disclosure relates to distributed monitoring systems for a structure.

DETAILED DESCRIPTION

In the drawings and description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawings are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present invention is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings.

Referring toFIGS. 1-3, an exemplary embodiment of a system100for monitoring an aircraft includes one or more sensors nodes102that are operably coupled to a central controller104by a network106. In an exemplary embodiment, the sensor nodes102are distributed within an aircraft108for monitoring one or more operational states of the aircraft that may, for example, include stresses, strains, temperatures, and pressures. In an exemplary embodiment, one or more of the sensor nodes102communicate the operational states of the aircraft108to the central controller106that is housed within the aircraft using, for example, a network106that may, for example, include a hard wired, fiber optic, infra red, radio frequency, packet data, acoustic, or other communication pathway.

In an exemplary embodiment, each sensor node102includes a power supply102athat is adapted to scavenge energy from the immediate environment. In an exemplary embodiment, the power supply102amay, for example, scavenge electromagnetic energy, solar energy, radio-frequency energy, vibrational energy, heat energy, wind energy, radiated electromagnetic and/or other forms of energy from the environment. In an exemplary embodiment, the power supply102afurther includes a rechargeable battery102aaoperably coupled thereto. In this manner, short bursts of energy that may be scavenged can be scavenged by the power supply102aand stored for later use in the battery102aa. In an exemplary embodiment, the power supply102ais operably coupled, and supplies power, to a communication link102b, a switch102c, a micro-controller102d, a signal conditioner102e, a sensor102f, a switch102g, a switch102h, and a memory102i.

In an exemplary embodiment, the communication link102bis also operably coupled to the switch102cand adapted to transmit and receive communication signals between the sensor node102and the network106. In this manner, the sensor node102may communicate with other sensor nodes and the central controller104.

In an exemplary embodiment, the switch102cis also operably coupled to the communication link102band the micro-controller102dand adapted to be controlled by the micro-controller to thereby communications between the communication link and the micro-controller. In this manner, in the event that the micro-controller102ddetermines that communication should not occur between the communication link102band the micro-controller such as, for example, if the sensor node102lacks sufficient power, the micro-controller may operate the switch to prevent communication between the communication link and the micro-controller.

In an exemplary embodiment, the micro-controller102dis also operably coupled to the communication link102b, the switch102c, the signal conditioner102e, the sensor102f, and the switch102gfor monitoring and controlling the operation of each. In an exemplary embodiment, the micro-controller102dmay include, for example, a conventional general purpose programmable controller.

In an exemplary embodiment, the signal conditioner102eis also operably coupled to the micro-controller102dand the sensor102and adapted to condition signals transmitted by the sensor before they are further processed by the micro-controller. In an exemplary embodiment, the signal conditioner102emay, for example, include one or more conventional signal processing elements such as, for example, filters, amplifiers, and analog to digital converters.

In an exemplary embodiment, the sensor102fis also operably coupled to the signal conditioner102eand the switch102gand adapted to sense one or more operating conditions of the aircraft108in the immediate environment. In an exemplary embodiment, the sensor102fmay include, for example, one or more of the following: a strain gauge, a stress sensor, a temperature gauge, a pressure gauge, a radiation detector, a radar detector, a chemical sensor, a corrosion sensor and/or a detector of electromagnetic energy.

In an exemplary embodiment, the switch102gis also operably coupled to the micro-controller102dand the sensor102fand adapted to control the operation of the sensor under the controller of the micro-controller. In this manner, in the event that the micro-controller102ddetermines that the sensor102fshould not operate such as, for example, if the sensor node102lacks sufficient power, the micro-controller may operate the switch102gto prevent power from being supplied by the power supply102ato the sensor.

In an exemplary embodiment, the switch102his also operably coupled to the micro-controller102dand the communication link102band adapted to control the operation of the communication link under the controller of the micro-controller. In this manner, in the event that the micro-controller102ddetermines that the communication link102bshould not operate such as, for example, if the sensor node102lacks sufficient power, the micro-controller may operate the switch102hto prevent power from being supplied by the power supply102ato the communication link.

In an exemplary embodiment, the memory102iis also coupled to the micro-controller102din order to store the operating system of the sensor node102as well as other operating parameters and measurements taken by the sensor102f. The memory102imay, for example, include one or more conventional memory devices such as, for example, DRAMS, Flash memory, optical storage, hard disk drive, or other memory devices. In an exemplary embodiment, the memory102iis adapted to store at least one of the mechanical, electrical, chemical, bistable, or multi-stable states of the sensor102f.

Referring now toFIGS. 4aand4b, in an exemplary embodiment, one or more of the sensor nodes102of the system100implement a method400of operating in which, in402, the sensor node determines if there is any power available to the sensor node. If there is any power available to the sensor node102, then the sensor node determines if there is enough power available to the sensor node to permit the sensor node to execute at least one operation in404.

If there is enough power available to permit the sensor node102to execute at least one operation, then the sensor gets a listing of the possible operations given the amount of available power in406. The sensor node102then gets a listing of the current and next operational states for the sensor node in408.

The sensor node102then determines if the next operational states of the sensor node are included in the possible operations given the amount of available power in410. If the next operational states of the sensor node102are included in the possible operations given the amount of available power, then the sensor node executes the next operational states that are possible to execute given the amount of available power in412.

Referring now toFIGS. 5aand5b, in an exemplary embodiment, one or more of the sensor nodes102of the system100implement a method500of operating in which, in502, the sensor node determines if there is any power available to the sensor node. If there is any power available to the sensor node102, then the sensor node determines if there is enough power available to the sensor node to permit the sensor node to execute at least one operation in504.

If there is enough power available to permit the sensor node102to execute at least one operation, then the sensor gets a listing of the possible operations given the amount of available power in506. The sensor node102then gets a listing of the current and next operational states for the sensor node in508.

The sensor node102then determines if the next operational states of the sensor node are included in the possible operations given the amount of available power in510. If the next operational states of the sensor node102are included in the possible operations given the amount of available power, then the sensor node executes the next operational states, based upon their pre-determined priority, that are possible to execute given the amount of available power in512.

Referring now toFIG. 6, an exemplary embodiment of a system600for monitoring an aircraft is substantially identical in design and operation as the system100with the addition of a power dispenser and conditioner602that is operably coupled to a source of raw power604, a power manager606, a power allocator608.

In an exemplary embodiment, the source of raw power608may include one or more of the power supplies102aof one or more of the sensor nodes102. In an exemplary embodiment, the power dispenser and conditioner602is adapted to receive time varying raw power, P(t)raw, from the source of raw power604, condition the raw power, and then transmit time varying available power, P(t)avail, to the power allocator608. In an exemplary embodiment, the power dispenser and conditioner602includes one or more elements for conditioning the raw power such as, for example, a rectifier, a filter, and a regulator.

In an exemplary embodiment, the power manager606includes a power monitor606aand a power controller606b. In an exemplary embodiment, the power monitor606ais operably coupled to the output of the power dispenser and conditioner602for monitoring the available power, P(t)avail. In an exemplary embodiment, the power monitor606ais also operably coupled to the power controller606bfor communicating the available power, P(t)avail, to the power controller. In an exemplary embodiment, the power controller606bis also operably coupled to the power allocator608for controlling the operation of the power allocator.

In an exemplary embodiment, the power allocator608includes one or more allocators608ithat are each coupled to one or more elements of the sensor node102for controllably supplying power to the corresponding elements of the sensor node. In this manner, the power manager606and the power allocator608collectively determine the power available to the sensor node102and then allocate the available power to the elements of the sensor node.

In an exemplary embodiment, the system600may implement one or more aspects of the methods400and500, described and illustrated above with reference toFIGS. 4a,4b,5a, and5b. In an exemplary embodiment, the elements and functionality of the power dispenser and conditioner602, the raw power source604, the power manager606, and the power allocator608may be provided within one or more of the sensor nodes102and/or provided within the central controller104.

Referring now toFIG. 7, an exemplary embodiment of a system700for monitoring an aircraft is substantially identical in design and operation as the system600except that the power allocator608is omitted and the functionality formerly provided by the power allocator is provided by the micro-controller102dwithin the sensor nodes102.

In particular, in the system700, the power controller606bis operably coupled to the micro-controller102dof the sensor node102for directing the allocation of the available power by the micro-controller to the elements of the sensor node.

In an exemplary embodiment, the system700may implement one or more aspects of the methods400and500, described and illustrated above with reference toFIGS. 4a,4b,5a, and5b. In an exemplary embodiment, the elements and functionality of the power dispenser and conditioner602, the raw power source604, and the power manager606may be provided within one or more of the sensor nodes102and/or provided within the central controller104.

Referring now toFIG. 8, in an exemplary embodiment, one or more of the systems100,600, and700may implement a method800of operating in which, in802, the sensor nodes102are placed into a default mode of operation which may, for example, include a sleep mode in which the sensor node is inactive, a fully active mode in which the sensor node is fully active, or one or more intermediate active modes in which the sensor node has functionality that is less than in the fully active mode. In804, the system,100,600, or700, will then determine the amount of power available to the system. In an exemplary embodiment, in806, the system,100,600, or700, will then determine the available operational states of the sensor nodes102of the system given the amount of power available to the system.

In an exemplary embodiment, in808, the system,100,600, or700, will then determine the quality of the possible monitoring of the aircraft108given the available operational states of the sensor nodes102of the system given the amount of power available to the system. In an exemplary embodiment, the quality of the possible monitoring of the aircraft108may be a function of what monitoring is adequate based upon the operating envelope and actual operating condition of the aircraft. For example, when the aircraft108is cruising at high altitudes with minimal turbulence, the level of detail and sampling rate in the monitored conditions may be less than when the aircraft is climbing to, or diving from, altitude with heavy turbulence.

In an exemplary embodiment, in810, the system,100,600, or700, will then modify the operational states of the sensor nodes102in order to optimize one or more of: 1) the available operational states of the sensor nodes, 2) the volume of data collected by the sensor nodes, 3) the sampling rate of the data collected by the sensor nodes, 4) the communication throughput of data within the network106, and/or 5) the quality of the possible monitoring.

In an exemplary embodiment, during the operation of the systems,100,600and/or700, the switches,102c,102gand102h, may be operated by the micro-controller102dto place the sensor node102in a sleep mode by not permitting operation of the communication link102band the sensor102f. In this manner, the use of power by the sensor node102is minimized.

In an exemplary embodiment, during the operation of the systems,100,600and/or700, the sensor node102may be operated in a sleep mode of operation that may, for example, include a range of sleeping mode that may vary from a deep sleep to a light sleep. In an exemplary embodiment, in a deep sleep mode of operation, the sensor node102may be completely asleep and then may be awakened by a watch dog timer, external interrupt, or other alert. In an exemplary embodiment, in a light sleep mode of operation, some of the functionality of the sensor node102may be reduced. In an exemplary embodiment, in one or more intermediate sleeping modes of operation, the functionality of the sensor node102will range from a light sleep to a deep sleep.

In an exemplary embodiment, in one or more of the systems100,600and700, one or more of the elements and functionality of the power dispenser and conditioner602, the raw power source604, the power manager606, and the power allocator608may be provided within a sensor node102, within one or more groups of sensor nodes, and/or within the central controller104.

In an exemplary embodiment, in one or more of the systems,100,600and700, one or more of the elements and functionality of the raw power source604may be provided within a single sensor node102, within one or more groups of sensor nodes, or by all of the sensor nodes. For example, if the power supply102ain each of the sensor nodes102within one of the systems,100,600or700, is a solar cell, then the level of solar energy at each sensor node102will vary as a function of its location on the aircraft108. In an exemplary embodiment, the allocation of power within the sensor nodes102of the systems,100,600and700, will determine the mapping of the power generated by the sensor nodes and then allocate power among the sensor nodes in order to optimize the operation of the systems in monitoring the aircraft108.

In an exemplary embodiment, in one or more of the systems100,600and700, one or more of the sensor nodes102may provide one or more of the elements and functionality of the central controller104.

In an exemplary embodiment, one or more of the systems100,600and700, may be operated to provide an optimal quality of the possible monitoring of the aircraft108by placing one or more determined sensor nodes102into a sleep mode, even in the presence of adequate power to operate the determined sensor nodes if the systems determine that the optimal quality of the possible monitoring of the aircraft can still be achieved. In this manner, the determined sensor nodes102placed into a sleep mode may do one or more of: store power or store data within the determined sensor node. In this manner, data may be warehoused within a sensor node102for later use and/or power may be stored within the sensor node for later use.

In an exemplary embodiment, one or more of the systems100,600and700, may be operated to place one or more determined sensor nodes102into a sleep mode if the data for the determined sensor node may be extrapolated using the data available for adjacent sensor nodes.

Referring now toFIG. 9, an exemplary embodiment of a system900for monitoring an aircraft is substantially identical in design and operation as the system100except that an energy radiator902is positioned proximate the aircraft108and a central controller904is operably coupled to the network106.

In an exemplary embodiment, the energy radiator902includes one or more radiators of energy such as, for example, electromagnetic energy, solar energy, radio-frequency energy, vibrational energy, heat energy, and/or wind energy. In this manner, the energy radiator902may permit the power supplies102aof the sensor nodes102to scavenge energy for operating the sensor nodes from the energy radiated by the energy radiator902.

In an exemplary embodiment, the central controller904is operably coupled to the network106in order to monitor and control the operation of the sensor nodes102. In an exemplary embodiment, the central controller904may include a plurality of central controllers positioned proximate the aircraft100.

Referring toFIG. 10, in an exemplary embodiment, the system900implements a method1000of monitoring an aircraft in which, in1002, selected ones of the sensor nodes102are radiated with energy by operating the energy radiator902. In an exemplary embodiment, the amount of energy radiated in1002is selected to provide at least a threshold level of energy that may be scavenged by the selected sensor nodes102thereby permitting a predetermined level of desired functionality to be achieved by the sensor nodes.

In1004, the selected ones of the sensor nodes102scavenge the radiated energy using the power supplies102. In an exemplary embodiment, at least some of the scavenged radiated power is stored in a power storage battery provided in at least some of the power supplies. In this manner, a relatively short burst of radiated energy may provide functionality of the selected sensors nodes102for an extended period of time.

In an exemplary embodiment, the method1000is implemented as part of a static test of the aircraft108while the aircraft is housed within a hangar.

In an exemplary embodiment, the energy radiator902may radiate electromagnetic energy using a planar wave whose energy level does not decay substantially with distance. In an exemplary embodiment, the energy radiator902may include a phased array antenna for radiating energy. In an exemplary embodiment, the energy radiator902may include an arbitrarily large antenna and/or one or more directional antennas.

In an exemplary embodiment, the energy radiator902may radiate a large enough pulse of energy such that the batteries102aaof the power supplies102of the sensor nodes102are fully charged such that continued static testing of the aircraft108may continue with or without the need for further radiation of energy to the sensor nodes.

In an exemplary embodiment, the energy radiator902may include a light source operably coupled to a leaky fiber optic cable or light pipe that is positioned proximate the sensor nodes102to which it is desired to radiate energy. In an exemplary embodiment, the energy radiator902may include a source of thermal energy that may create temperature gradients within the aircraft108that may be used by the power supplies102aof the sensor nodes102to generate energy.

In an exemplary embodiment, the energy radiated by the energy radiator902is selected to include forms of energy that will not effect the structure and/or the measurements to be taken of the aircraft100.

Referring toFIG. 11, in an exemplary embodiment, the system100implements a method1100of monitoring an aircraft in which, in1102, the sensor nodes102scavenge sufficient energy from the local environment to permit the sensors102fof the sensor nodes to sense one or more operating conditions and store the measured operating condition within the sensor and/or the memory102i. In an exemplary embodiment, in1102, the sensors102fof the sensor nodes102recognize that a threshold measured value has been obtained and thereby latch to that sensed value

In an exemplary embodiment, as illustrated inFIG. 12, the sensors102fof the sensor nodes102are provided with one or more stable operating states that are each reflective of a value of an operating condition. For example, as illustrated inFIG. 12, one or more of the sensors102fof the sensor nodes102may include an initial operating state S0. Upon the sensing of an operating condition, which would include some form of input energy to the sensor102f, the operational state may then change to a stable sensed state S1. The sensor102fof the sensor node102would remain in this stable latched operational state unless and until another event reflective of a change in operating conditions, which would include some form of input energy to the sensor102f, occurred which would move the sensor to a new stable operational state S2. In this manner, the sensor102fof the sensor102would latch onto the sensed operational state and the sensor could be a mechanical latch and/or an electronic latch. In an exemplary embodiment, the number of stable operational states could be any value and such value could determine the level of granularity in the sensor102f. In an exemplary embodiment, the number of stable operational states also may be used to provide an electrical and/or mechanical analog to digital converter in which the number of stable operational states of the sensor102fdetermines the number of levels in the analog to digital converter.

In an exemplary embodiment, the sensors102fof one or more of the sensor nodes102are further adapted to stored measure values of operating conditions using the energy associated with the operating condition itself. In this manner, the sensors102fare able to store stored measure values of operating conditions using the energy associated with the operating condition for indefinite periods of time. For example, as illustrated inFIG. 12, the sensor102fmay include one or more stable operating states that are each entered into by injecting energy into the sensor, where the injected energy is the operating condition being measured.

In an exemplary embodiment, in1104, sensor nodes102are then radiated with energy in sufficient amounts to permit the sensor nodes to transmit the stored measurements and to reset the sensors102f. In an exemplary embodiment, in1104, as illustrated inFIG. 13, the sensor nodes102are radiated with energy in sufficient amounts to permit the sensor nodes to transmit the stored measurements by operating an energy radiator1302proximate the sensor nodes. In an exemplary embodiment, the design and operation of the energy radiator1302is substantially the same as the energy radiator902.

In an exemplary embodiment, in1106, the sensor nodes102scavenge the radiated energy using the power supplies102. In an exemplary embodiment, at least some of the scavenged radiated power is stored in a power storage battery provided in at least some of the power supplies. In this manner, a relatively short burst of radiated energy may provide functionality of the selected sensors nodes102for an extended period of time. In an exemplary embodiment, in1106, the sensor nodes102scavenge the radiated energy using the power supplies102in sufficient amount to permit the sensor nodes to transmit the stored measurements and to reset the sensor102f.

In an exemplary embodiment, in1108, the sensor nodes102determine whether to transmit the stored measurements or, in the alternative, to transmit the stored measurements and then reset the sensor102f. In an exemplary embodiment, each sensor102will be programmed by a user of the system100in order to determine which action should be taken. Alternatively, the desired action to be taken may be altered by downloading instructions to the sensor nodes102and/or may be adaptively determined as a function of the type or location of the sensor102fof the sensor node, the magnitude of the stored measurements, or other factors.

If a particular sensor node102has been instructed to only transmit the stored measurements, then, in1110, the sensor node will only transmit the stored measurements to one or more of the central controllers104. In an exemplary embodiment, in1110, the transmission of the stored measurements by the sensor node may be a singlecast or multicast transmission, and may, for example, be transmitted using data packets protocols.

If a particular sensor node102has been instructed to transmit the stored measurements and reset the sensor102f, then, in1112, the sensor node will transmit the stored measurements to one or more of the central controllers104and then the sensor node102will then reset the associated sensor102fin1114. In an exemplary embodiment, in1112, the transmission of the stored measurements by the sensor node may be a singlecast or multicast transmission, and may, for example, be transmitted using data packets protocols. In an exemplary embodiment, in1114, the sensor102node102will reset the sensor102fby, for example, resetting the operational state of the sensor to an earlier operational state.

In an exemplary embodiment, as illustrated inFIG. 13, in1110and/or1112, the sensors102and/or the central controllers104may transmit the stored measurements to one or more external central controllers1304. In an exemplary embodiment, the energy radiator1302may include, or at least be operably coupled to, the central controller1304. In this manner, a portable device that may include both the energy radiator1302and the central controller1304may be used to wand over selected sensor nodes102to thereby interrogate the sensor nodes, capture the stored measurements contained therein, and, if required, also reset the sensors102fin one or more of the selected sensor nodes102.

In an exemplary embodiment, after completing1110and/or1112, one or more of the central controllers104may send an acknowledgement to the sensor node102that transmitted the stored measurements and, in an exemplary embodiment, upon the receipt of the acknowledgement by the sensor node, the sensor node will reset the sensor node's operational state.

In an exemplary embodiment, the method1100may be used, for example, to provide a regular diagnostic program for the aircraft108by mounting the energy radiator1302and the central controller1304at a fixed location such as, for example, in the ceiling of an aircraft hangar. Then, as the aircraft108is moved into or out of the hangar, the stored measurements within the sensors102fof the sensor nodes102may be extracted for processing by the central controller1304to determine the health of the aircraft.

In an exemplary embodiment, the method1100may be used, for example, to provide a regular diagnostic program for a carrier based aircraft108by mounting the energy radiator1302and the central controller1304at a fixed location such as, for example, the aircraft elevator on the carrier. Then, as the aircraft108is moved onto or off of the deck of the carrier, the stored measurements within the sensors102fof the sensor nodes102may be extracted for processing by the central controller1304to determine the health of the carrier based aircraft.

It is understood that variations may be made in the above without departing from the scope of the invention. For example, the teachings of the exemplary embodiments may be applied to monitoring an aircraft, a ship, a vehicle, a building, the environment, or any other application in which a distributed monitoring system would provide value. While specific embodiments have been shown and described, modifications can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments as described are exemplary only and are not limiting. Many variations and modifications are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.