Synched E Harvesting Wireless Sensors For Sensors Expo 2009 Dist

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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.

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Synched E Harvesting Wireless Sensors For Sensors Expo 2009 Dist

  1. 1. Synchronized Energy Harvesting Sensor Networks S.W. Arms*, J.H. Galbreath, C.P. Townsend, D.L. Ch hill N D L Churchill, Nam Ph ^ Phan^ * President, CEO ^Division Head (Acting) Structures MicroStrain, MicroStrain Inc Structures Division - AIR 4 3 3 2 4.3.3.2 Williston, Vermont Naval Air Systems Command www.microstrain.com Patuxent River, Maryland swarms@microstrain.com. Proc. Sensors Expo, Rosemount, IL, June 9h, 2009 © microstrain, inc. 2009 all rights reserved
  2. 2. Sensing the Future Wireless sensors, in the billions, will become deeply embedded within structures & machines. Sensed information will be automatically compressed & forwarded for condition based maintenance. © microstrain, inc. 2009
  3. 3. The Economist April 28th – May 4th 2007 “We’re wearing out…plan to replace us soon”
  4. 4. Problem: But h B who will replace all ill l ll those dead batteries? © microstrain, inc. 2009
  5. 5. Solution: • Harvest & store energy from strain strain, vibration, vibration, motion, thermal gradients, light, electromagnetic fields light • Use power management to balance the energy “checkbook” “checkbook” • Use embedded processors to compress data, data compute fatigue life © microstrain, inc. 2009
  6. 6. Bell M412 Installation Strain energy harvesting wireless pitch link installed on Bell M412 Feb 2007 (1st time ever) Patents pending © microstrain, inc. 2009
  7. 7. Flight Test Results • Passed – in-flight EMI evaluations in- – rotor track & balance verification • Data were collected wirelessly on board the aircraft with no indication of data loss Patents pending © microstrain, inc. 2009
  8. 8. Objective: Demonstrate a synchronized, energy harvesting, wireless structural health harvesting monitoring & reporting system for helicopters © microstrain, inc. 2009 Patents pending
  9. 9. Detailed D t il d Objectives • Develop a wireless data aggregator (WSDA), capable of synchronizing wireless/hard-wired sensor networks and wireless/hard- aggregating data with open architecture communications to HUMS HUMS. • Document time synchronization accuracy • Develop a high sample rate wireless sensor node for helicopter gearbox apps. • Demonstrate system compatibility with a scalable network of active RFID t k f ti RFIDs.
  10. 10. Communicatingg Wirelessly y
  11. 11. MicroStrain’s Wireless Sensor Networks (IEEE 802.15.4) ( 802.15. Time Division Multiple Access Frequency Division ( (TDMA) & ) Multiple Access (FDMA) Carrier Sense Multiple Access (CSMA) © microstrain, inc. 2008
  12. 12. How many nodes will this low power TDMA system support? Aggregate sample rate (Hz): ~10,000/total no. sensor channels 10 000/total no i.e.: ~100 single ch nodes can i 100 i l h d transmit data at 100 samples/sec Patents pending © microstrain, inc. 2008
  13. 13. Methods: Timing Engine
  14. 14. Previous Work • Le Cam, V., “Synchronization of Wireless Sensors: Review of Methodologies, Experience Feedback of the Very Precise GPS Solution”, Third European Workshop Solution on Structural Health Monitoring, July 5-7, Granada, 5- Spain, July 5-7, 2006 5- Placed GPS receivers at each wireless node to achieve absolute precision of 1 microsecond
  15. 15. Data Aggregator collects gg g time synchronized data w/ 4 GB removable flash memory 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 Data Aggregator. Data Aggregator’s RTC uses Global Positioning System ’ C Gl b l S (GPS) as time reference. Data Aggregator sends beacons to update time sensing node’s time keepers p g p Patents pending © microstrain, inc. 2009
  16. 16. Timing Engine Overview • Timing Ti i engine provides th i id the following: GPS • 1pulse per second Receiver CAN CAN Nodes CAN Nodes CAN Nodes CAN Nodes (PPS) Synch Clock Controller • Trigger Line Timing Ti i Wireless Wireless Nodes • Extremely accurate Engine Controller Wireless Nodes Wireless Nodes Wireless Nodes absolute time keeper • The 1 PPS synchronization y Wireless Wireless Nodes Wireless N d Wi l clock is distributed to CAN Controller Wireless Nodes WirelessNodes Nodes and 802.15.4 network 802.15. controllers. (green) µP Core running Linux USB Node SYNCH CLK & TRIG • In turn, network controllers turn USB N d Node CAN Synch Mechanism propagate the 1PPS clock to nodes through a high-priority high- RS-232 Node Wireless Synch Beacon broadcast beacon packet. RS-232 Node (blue and orange) Patents pending © microstrain, inc. 2009
  17. 17. Harvesting g Energy gy
  18. 18. Vibration vs. Strain Energy Harvesters: gy Gearbox Resonant Energy G b R tE Harvester Output: 37 mW Volume: 4.3 cc Weight: 38 grams Flexible Strain Harvester Output: ~14 uW per sq cm (90 uW per sq in) @ 200 uE p-p, 4.3 Hz p p, On Bell 412 Pitch Link 12 patches delivered ~ 1 uW/lb (200-400 uW) Weight: 4.3 gr/patch*12 patches = 52 gr Patents pending © microstrain, inc. 2009
  19. 19. Sensing strain strain, force, pressure, force pressure torque, vibration, torque vibration temperature Wirelessly
  20. 20. MicroStrain’s embedded firmware optimized for strain gauges • Wireless offset adjust • Wireless gain adjust • Wireless co t o o sa p e rates e ess control of sample ates • Wireless shunt cal – bits to microstrain • Low tempco’s: tempco s tempco’s:s: offset: -.007%/C , span: .015%/C 015%/C • Mux’d, pulsed & regulated bridge excitation Mux dd, Patents pending © microstrain, inc. 2009
  21. 21. Wireless Pitch Link Strain & Load Sensing Nodes Fractal antennas Shear-Link ™ © microstrain, inc. 2009 Patents Pending
  22. 22. Pitch Link Consumption for Various Operating Modes: O ti M d • Mode 1: Wait until stored energy crosses threshold: nanoamp threshold: comparator turns circuit “on”. Predetermined amount of data transmitted. Consumption varies with available energy, timekeeper draws 9 microwatts. • Mode 2: Data logged to memory: Download at end of test. Consumption @ 32 samples/sec: ~100 uwatts • Mode 3: Transmit if energy allows: Log 100 samples, check stored energy, transmit if possible. Consumption with 32 samples/sec: ~250 uW, uW, drops to 100 uW without radio transmission. • Mode 4: Real Time Transmission: Log 100 samples, then transmit. Consumption with 32 samples/sec: ~250 uwatts. uwatts. © microstrain, inc. 2009 Patents pending
  23. 23. Wireless Bridge (Strain) System Di S t Diagram Time keeper (patents pending) © microstrain, inc. 2009
  24. 24. High Speed Wireless Node • Programmable sample rates, g p offsets, offsets, gains, & anti-aliasing anti- filters • A/D resolution: 16 bits • 100 KHz A/D sampling rate (3 ch, ch, simultaneous, full diff) • Event consists of 125,000 samples (or 0.4 seconds at 100 KHz sample rate) • Stores 1 million samples on 2 MB embedded, non-volatile memory Patents Pending © microstrain, inc. 2009
  25. 25. Energy Conservation: work to balance the “energy checkbook” “ h kb k” © microstrain, inc. 2009
  26. 26. Powering down between g samples greatly reduces power consumption Patents pending © microstrain, inc. 2009
  27. 27. Embedded routines allow microelectronics to adapt to the th amount of available t f il bl energy © microstrain, inc. 2009 Patents pending
  28. 28. Average power consumption g p p (mW) for 50 kSPS data mW) acquisition i iti Acquisition Interval Sample 1 min 10 min 1 hour 1 day y duration (sec) 0.1 1.67 0.22 0.09 0.06 0.5 8.09 0.86 0.19 0.07 1.0 10 16.1 16 1 1.66 1 66 0.33 0 33 0.07 0 07 © microstrain, inc. 2009
  29. 29. Results: Wireless Network Timing - How quickly are broadcast commands processed?
  30. 30. Broadcast Synchronization Results (4 nodes) • Waveform at right shows g Scope traces 4 captured waveforms representing the start of sampling for each of the 4 p g nodes. • Note that each node starts sampling at slightly different times. In this specific case the last case, node started sampling ~3.4 microseconds (µsec) after the first node node. © microstrain, inc. 2009
  31. 31. Broadcast Synchronization Results Scope traces • After repeating the broadcast trigger command 250 times, the d ti th timing differences are bound within an envelope of ±4 µsec. This represents the initial synchronization accuracy for the group of nodes. © microstrain, inc. 2009
  32. 32. Results: Wired & Wireless Network Timing: How well synced w/ beaconing? g
  33. 33. Saw tooth Input, room temp. 2 nodes, 2 h d hours @ room t temperature, t clock drift: ~325 us (45 ppb) between the two sensor nodes Timing beacon sent once – at start of test only. Node 1 & Node 2  Sensor Data Overlay  3 2.5 ensor Input (V) 2 1.5 1 Se 0.5 0 7199.94 7199 94 7199.96 7199 96 7199.98 7199 98 7200.00 7200 00 7200.02 7200 02 7200.04 7200 04 7200.06 7200 06 7200.08 7200 08 Time (seconds) © microstrain, inc. 2009
  34. 34. Saw Tooth Input, -40 to +85 deg C 2 nodes 2 hours w/ 10 Hz Sawtooth: clock drift 5.71 msec (793 ppb) nodes, hours, 5 71 w/ 1 Hz Sawtooth: clock drift 5.04 msec (700 ppb) Timing beacon sent once – at start of test only. Node 1 & Node 2  Sensor Data Overlay  3 2.5 Sensor Input (V) 2 1.5 1 0.5 0 7199.70 7199.72 7199.74 7199.76 7199.78 7199.80 7199.82 7199.84 Time (seconds) © microstrain, inc. 2009
  35. 35. Timing Results Summary • Synch 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 when sub-millisecond temperatures are extreme and changing rapidly. © microstrain, inc. 2009
  36. 36. Conclusions • Accurate time synch developed for wireless sensor nets that doesn’t require GPS. • System supports high sample rate (50 KHz) sensor nodes, and active RFID tags • Provides open architecture interface to HUMS to eliminate wires and enable reductions in weight and complexity. Patents pending © microstrain, inc. 2009
  37. 37. Conclusions (continued) • High sample rate nodes can operate perpetually, without batteries, from gearbox vibration alone. • Supports remote reporting over mobile phone networks (satellite reporting currently under development). development) • These capabilities, coupled with appropriate wireless security methods, will enable critical structural sensor data to be managed remotely, securely, and automatically. Patents pending © microstrain, inc. 2009
  38. 38. Need More Info? • Sensors Expo Booth 1005 • www.microstrain.com • www.microstrain.com/customer-docs.htm www.microstrain.com/customer- • swarms@microstrain.com @
  39. 39. Acknowledgements: Navy/NAVAIR SBIR PH II ONR BAA Bell Helicopter p Thank You!
  40. 40. References: • M.J. Hamel et al., Energy Harvesting for Wireless Sensor Operation and Data Transmission, US Patent Appl. Publ. US 2004/0078662A1, filed March 2003 • D L Churchill et al., Strain Energy Harvesting for Wireless Sensor Networks, D.L. Ch hill l S i E H i f Wi l S N k Smart Structures and Materials, SPIE, vol. 5005, pp. 319–327, 2003 • S.W. Arms et al., Shaft Mounted Energy Harvesting System for Wireless g g Sensor Operation and Data Transmission, US Patent Appl. Publ. US d l bl 2005/0017602A1, filed Jan 2004 • S.W. Arms et al., Wireless Strain Measurement Systems for Aircraft Test, , y Test, 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 2006 g, p y , , , y • S.W. Arms, C.P. Townsend, D.L. Churchill, M. Augustin, D.Yeary, P. Darden, Augustin, D.Yeary, N. Phan, Tracking Pitch Link Dynamic Loads with Energy Harvesting Wireless Sensors, AHS 63 d Annual Forum, Virginia Beach, VA, May 2007 S 63nd A lF Vi i i B h VA M

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