Miniaturized Wireless Sensing for Process Monitoring

Transcription

1 Miniaturized Wireless Sensing for Process Monitoring Prof. Brian Otis, Prof. Babak Parviz University of Washington Electrical Engineering Department Seattle, WA, USA

2 Outline Motivation: inexpensive, microscale wireless process monitors Technical challenges New results: 500mg wireless temperature sensor

3 Goal: improved process observability using distributed sensors

4 From the large scale Example: Structural monitors, fluid conductivity, flow rate, temperature, etc, at arbitrary locations Unrealistic to position thousands of complete sensing and chemical analysis units Use large number of inexpensive wireless monitors Network density provides high spatial resolution and robustness

5 to the micro scale Dense networks of interconnected wireless sensors Allow fine grained measurement of process parameters Sub mm device sizes * Prof. Albert Folch, University of Washington

6 Challenges: cost, size, power Necessary to integrate many different technologies in a very small volume: Various sensors RF transceiver/antenna Microprocessor Battery/Power supply Passive components NI Data Acquisition Card The resulting system: Too large for microscale sensing Prohibitively expensive for ubiquitous deployment Power is a huge problem

7 Moore s Law to the rescue : 25um MOS process Today: 0.032um MOS process The number of transistors on an IC doubles every 2 years Resulting from advancements in IC fabrication and design automation

8 Why is this important? 1. Computation and signal processing can now be performed in a few mm 2 2. This computational power is growing exponentially 3. Scientists in many communities (wildlife tracking, process monitoring, neural engineering) are recognizing this and are eager to take advantage of this opportunity 4. Can enable previously impossible collection of data

9 We can shrink the electronics But what about power? Battery technology can t keep pace with Moore s law Towards energy harvesting for autonomous sensors...

10 Energy harvesting Extract energy from the environment to power wireless sensors S. Roundy, B. Otis, Y.H. Chee, J. Rabaey, P. Wright, IEEE ISLPED 2003 Good candidates for process monitors: RF, solar, thermal, vibrational.

11 Thermal power Battery replacement: 1cm 3 footprint 10uW average power Provide heat flow sensing? 1cm

12 Wireless power transfer sensor Detect Asymmetric link: shifts burden of power and complexity to the interrogator Allows very small, inexpensive sensing tags

13 Case study: a wireless temperature sensor Goal: miniaturized, battery free, wireless sensor for monitoring temperature levels in chemical processes, pipelines, and storage tanks Also applicable to automotive, aviation, industrial, and medical monitoring

14 Wireless sensor architecture Wireless power + RFID circuitry 1 10m Sensor ID, Data RFID reader RFID + sensor tag

15 The power challenge Temperature sensing requires precision amplification and analog to digital conversion (ADC) Unstable power supply due to wireless power transfer Digital computation required for processing the RFID protocol The range and functionality of the system is limited by the amount of power that can be wirelessly transferred

16 Prototype electronics

17 Wireless sensor platform Power provided wirelessly from 900 MHz commercial RFID tag reader: 1m range Maintenance free Energy is stored on the board to power sensor interface Custom low noise IC

18 Initial deployment: wireless neural interface Use commercial 900MHz RFID reader Communication through EPC Gen2 protocol Single channel far field neural recording device 1m range J. Holleman, D. Yeager, R. Prasad, J.R. Smith, and B. Otis, BioCAS, November 2008

19 Initial deployment: wireless neural interface Example: wireless EMG recording on a hawkmoth Spike detector Returns spike count instead of electronic product code (EPC) Low noise amp Can digitize and transmit short bursts of data after triggering Wireless charging Sensing (RF Off) Backscatter data

20 Current research: miniaturization Integration of RF, sensor interface, and computation onto a single integrated circuit

21 SoC WISP 1mm x 2mm <10μW power dissipation Assembly completed 7/22/2009 Single chip wirelessly powered sensor interface 0.13μm CMOS ~ 100,000 transistors Dimensions: 1mm x 2mm x 0.15mm Designers: Dan Yeager Azin Zarrasvand Helen Zhang

22 SoC WISP 2μW chopper stabilized amplifier 8 bit analog to digital converter RF energy harvester Three voltage regulators (0.7V, 1.2V, 1.8V) Digital RFID Gen2 protocol Unique chip identification generator Supply/process independent 8MHz oscillator

23 RF Energy Harvesting Performance Sufficient operating voltage at an input RF power of 16dBm (~25μW)

24 Wirelessly powered temp sensor Connection to generic thermocouple allows wireless, battery free temperature sensing ~ 500mg including antenna Range: ~2m with standard commercial RFID reader We ve developed a GUI allowing programmable averaging and data logging

25 Wirelessly powered temp sensor Connection to generic thermocouple allows wireless, battery free temperature sensing ~ 500mg including antenna Range: ~2m with standard commercial RFID reader We ve developed a GUI allowing programmable averaging and data logging

26 Wirelessly powered temp sensor Connection to generic thermocouple allows wireless, battery free temperature sensing ~ 500mg including antenna Range: ~2m with standard commercial RFID reader We ve developed a GUI allowing programmable averaging and data logging ~40 reads/second Adjustable averaging Real-time readout

27 Miniaturized flight recorder for hawkmoths DLM s Longitudinal section of Manduca sexta Initial deployment: recording temperature in flight from the Dorsolongitudinal (DLM) Muscles (main muscles that indirectly power the downstroke of the wings) Allows recording of previously impossible data Collaboration with Nicole George, Prof. Tom Daniel, UW Biology

28 Conclusions 1. Moore s law: exponential growth in computational power 2. There s also a dramatic growth in performance of wireless sensing technologies 3. We have demonstrated early prototypes of a few key technologies 4. Recent results: battery free wireless temperature sensor integrated circuit