This presentation, "Synchronized Energy Harvesting Sensor Networks", was made at the 2009 Sensors Expo in Rosemount, IL. MicroStrain has developed the next generation energy harvesting wireless nodes for health monitoring of structures and condition based monitoring of machinery. These nodes can be integrated into a large scale network, controlled with a Wireless Sensor Data Aggregator (WSDA) providing node-to-node synchronization up to +/- 4 microseconds.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Synchronized Energy Harvesting Sensor Networks
S.W. Arms*, J.H. Galbreath, C.P. Townsend,S.W. Arms*, J.H. Galbreath, C.P. Townsend,D L Ch hill N Ph ^D L Ch hill N Ph ^D.L. Churchill, Nam Phan^D.L. Churchill, Nam Phan^
^Division ^Division Head (Acting) Head (Acting) StructuresStructuresStructures DivisionStructures Division AIR 4 3 3 2AIR 4 3 3 2
Sensing Sensing the Futurethe Futurethe Futurethe Future
Wireless sensors, in the billions, will become Wireless sensors, in the billions, will become deeply embedded within structures & deeply embedded within structures & machines. machines.
Sensed information will be automatically Sensed information will be automatically compressed & forwarded for condition compressed & forwarded for condition based maintenance.based maintenance.
B hB h ill lill l llllBut who But who will replace will replace all all thosethose dead batteries?dead batteries?those those dead batteries?dead batteries?
Solution:Solution:Solution:Solution:•• HarvestHarvest & store energy from strain& store energy from strain•• Harvest Harvest & store energy from strain, & store energy from strain,
•• UseUse power management to balance thepower management to balance the•• Use Use power management to balance the power management to balance the energy “checkbookenergy “checkbook””
•• Use Use embedded processors to compress embedded processors to compress data computedata compute fatigue lifefatigue lifedata, compute data, compute fatigue life fatigue life
•• Data were collected wirelessly on board the Data were collected wirelessly on board the aircraft with no indication of data lossaircraft with no indication of data loss
Objective:Objective: Demonstrate a synchronized, Demonstrate a synchronized, energy harvesting wireless structural healthenergy harvesting wireless structural healthenergy harvesting, wireless structural health energy harvesting, wireless structural health monitoring & reporting system for helicopters monitoring & reporting system for helicopters
D t il dD t il dDetailedDetailedObjectivesObjectivesObjectivesObjectives
•• Develop a wireless data aggregator (WSDA), capable ofDevelop a wireless data aggregator (WSDA), capable ofDevelop a wireless data aggregator (WSDA), capable of Develop a wireless data aggregator (WSDA), capable of synchronizing wireless/hardsynchronizing wireless/hard--wired sensor networks and wired sensor networks and aggregating data with open architecture communications aggregating data with open architecture communications to HUMSto HUMSto HUMS.to HUMS.
•• Document time synchronization accuracyDocument time synchronization accuracy•• Develop a high sample rate wireless sensor node forDevelop a high sample rate wireless sensor node forDevelop a high sample rate wireless sensor node for Develop a high sample rate wireless sensor node for
helicopter gearbox apps.helicopter gearbox apps.•• Demonstrate system compatibility with a scalable Demonstrate system compatibility with a scalable
t k f ti RFIDt k f ti RFIDnetwork of active RFIDs.network of active RFIDs.
Previous WorkPrevious WorkPrevious WorkPrevious Work
•• Le Cam, V., “Synchronization of Wireless Sensors: Le Cam, V., “Synchronization of Wireless Sensors: Review of Methodologies, Experience Feedback of the Review of Methodologies, Experience Feedback of the Very Precise GPS Solution” Third European WorkshopVery Precise GPS Solution” Third European WorkshopVery Precise GPS Solution , Third European Workshop Very Precise GPS Solution , Third European Workshop on Structural Health Monitoring, July 5on Structural Health Monitoring, July 5--7, Granada, 7, Granada, Spain, July 5Spain, July 5--7, 20067, 2006
Placed GPS receivers at each wireless node Placed GPS receivers at each wireless node to achieve absolute precision of 1 to achieve absolute precision of 1 microsecondmicrosecond
All wireless nodes use precision nano-power real time clock p p(RTC) with +/- 3 ppm (-40 to +85 deg C) time reference.
Wired inertial sensor uses same time reference as DataWired inertial sensor uses same time reference as Data Aggregator.
’ C Gl b l SData Aggregator’s RTC uses Global Positioning System (GPS) as time reference. Data Aggregator sends beacons to update time sensing node’s time keepersp g p
SYNCH CLK & TRIG•• In turn, network controllers In turn, network controllers
propagate the propagate the 11PPS clock to PPS clock to nodes through a highnodes through a high--priority priority broadcast beacon packet. broadcast beacon packet. (blue and orange)(blue and orange)
Sensing strainSensing strain, force pressureforce, pressure, torque vibrationtorque, vibration,
temperaturetemperature
WirelesslyWirelessly
MicroStrain’s embedded firmware MicroStrain’s embedded firmware optimized for strain gaugesoptimized for strain gauges
•• Wireless offset adjust Wireless offset adjust •• Wireless gain adjustWireless gain adjust•• Wireless control of sample ratesWireless control of sample ratese ess co t o o sa p e atese ess co t o o sa p e ates•• Wireless shunt cal Wireless shunt cal –– bits to bits to microstrainmicrostrain•• LowLow tempco’stempco’s::•• Low Low tempco stempco s: :
Pitch Link Consumption for Various Pitch Link Consumption for Various O ti M dO ti M dOperating Modes:Operating Modes:
•• Mode 1: Wait until stored energy crosses thresholdMode 1: Wait until stored energy crosses threshold:: nanoampnanoamp•• Mode 1: Wait until stored energy crosses thresholdMode 1: Wait until stored energy crosses threshold: : nanoampnanoampcomparator turns circuit “on”. Predetermined amount of data comparator turns circuit “on”. Predetermined amount of data transmitted. transmitted. Consumption varies with available energy, timekeeper Consumption varies with available energy, timekeeper draws 9 microwatts.draws 9 microwatts.
•• Mode 2: Data logged to memory:Mode 2: Data logged to memory: Download Download at at end end of test. of test. Consumption @ 32 samples/sec: ~100 Consumption @ 32 samples/sec: ~100 uwattsuwatts
•• Mode 3: Transmit if energy allows:Mode 3: Transmit if energy allows: Log 100 samples, check stored Log 100 samples, check stored energy, transmit if possible. energy, transmit if possible. Consumption with 32 samples/sec: ~250 Consumption with 32 samples/sec: ~250 uWuW, drops to 100 , drops to 100 uWuW without radio transmission.without radio transmission.
•• Mode 4: Real Time Transmission:Mode 4: Real Time Transmission: Log 100 samples, then transmit. Log 100 samples, then transmit. Consumption with Consumption with 32 samples/sec: ~250 32 samples/sec: ~250 uwattsuwatts..
Powering down between Powering down between ggsamples greatly reduces samples greatly reduces power consumptionpower consumptionpower consumptionpower consumption
• Waveform at right shows Scope tracesg4 captured waveforms representing the start of sampling for each of the 4 p gnodes.
• Note that each node• Note that each node starts sampling at slightly different times. In this specific case the lastspecific case, the last node started sampling ~3.4 microseconds (µsec) after the first nodeafter the first node.
command 250 times, the timing differences are bound within an envelope of ±4 µsec. This represents the initial synchronization accuracysynchronization accuracy for the group of nodes.
• Synch beacon sent once at start of test only providedSynch beacon sent once - at start of test only - provided ~5 ms timing accuracy over 2 hours, subjected to -40 to +85 C.
• Synch w/ periodic (60 sec) beacon provided +/- 50 us timing accuracy over 13 hours, subjected to -40 to +85 C.g y , j
• Conservative approach: send resync beacon every 5 minutes to achieve sub millisecond timing accuracy whenminutes to achieve sub-millisecond timing accuracy when temperatures are extreme and changing rapidly.
•• Accurate time synch developed for wirelessAccurate time synch developed for wireless
Conclusions Conclusions
Accurate time synch developed for wireless Accurate time synch developed for wireless sensor nets that doesn’t require GPS.sensor nets that doesn’t require GPS.
•• System supports high sample rate (50 KHz) System supports high sample rate (50 KHz) sensor nodes, and active RFID tagssensor nodes, and active RFID tags
•• Provides open architecture interface to HUMS Provides open architecture interface to HUMS to eliminate wires and enable reductions into eliminate wires and enable reductions into eliminate wires and enable reductions in to eliminate wires and enable reductions in weight and complexity.weight and complexity.
•• High sample rate nodes can operateHigh sample rate nodes can operate
Conclusions (continued) Conclusions (continued)
•• High sample rate nodes can operate High sample rate nodes can operate perpetually, without batteries, from gearbox perpetually, without batteries, from gearbox vibration alone.vibration alone.
•• Supports remote reporting over mobile phone Supports remote reporting over mobile phone networks (satellite reporting currently under networks (satellite reporting currently under development)development)development). development).
•• These capabilities, coupled with appropriate These capabilities, coupled with appropriate wireless security methods, will enable criticalwireless security methods, will enable criticalwireless security methods, will enable critical wireless security methods, will enable critical structural sensor data to be managed remotely, structural sensor data to be managed remotely, securely, and automatically.securely, and automatically.
Navy/NAVAIR Navy/NAVAIR SBIR PH II SBIR PH II ONR BAAONR BAAONR BAA ONR BAA
Bell HelicopterBell Helicopterpp
Thank You!Thank You!
References:References:•• M.J. Hamel et al., Energy Harvesting for Wireless Sensor Operation and Data M.J. Hamel et al., Energy Harvesting for Wireless Sensor Operation and Data
Transmission, Transmission, US Patent Appl. Publ. US 2004/0078662A1, filed March US Patent Appl. Publ. US 2004/0078662A1, filed March 20032003
D L Ch hill l S i E H i f Wi l S N k• D.L. Churchill et al., Strain Energy Harvesting for Wireless Sensor Networks, Smart Structures and Materials, SPIE, vol. 5005, pp. 319–327, 2003
•• S.W. Arms et al., Shaft Mounted Energy Harvesting System for Wireless S.W. Arms et al., Shaft Mounted Energy Harvesting System for Wireless dd l bll bl
g gg gSensor Operation and Data Transmission, Sensor Operation and Data Transmission, US Patent Appl. Publ. US US Patent Appl. Publ. US 2005/0017602A1, filed Jan 2004 2005/0017602A1, filed Jan 2004
• S.W. Arms et al., Wireless Strain Measurement Systems for Aircraft TestWireless Strain Measurement Systems for Aircraft Test, , yy ,Aerospace Test Expo, Anaheim, CA, Nov 2006
• S.W. Arms et al., Energy Harvesting Wireless Sensors for Helicopter Damage Tracking, American Helicopter Society Annual Forum, Phoenix, AZ, May 2006g, p y , , , y
•• S.W. Arms, C.P. Townsend, D.L. Churchill, M. S.W. Arms, C.P. Townsend, D.L. Churchill, M. AugustinAugustin, , D.YearyD.Yeary, P. Darden, , P. Darden, N. Phan, N. Phan, Tracking Pitch Link Dynamic Loads with Energy Harvesting Wireless Tracking Pitch Link Dynamic Loads with Energy Harvesting Wireless SS AHS 63 d A l F Vi i i B h VA M 2007AHS 63 d A l F Vi i i B h VA M 2007Sensors, Sensors, AHS 63nd Annual Forum, Virginia Beach, VA, May 2007AHS 63nd Annual Forum, Virginia Beach, VA, May 2007