SPEEDY: A Fall Detector in a Wrist Watch

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SPEEDYA Fall Detectorin a Wrist Watch
Technology Leadership Day 2003

• Thomas Degen

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Content

• Motivation
• Concept
• Principles of Detection
• Results
• Conclusion
• Demonstration
• Outlook

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Motivation

• Health Monitoring is a very attractive
  application field for wearable computers
• The market for elderly people is growing in both
  numbers and economic figures
• Existing fall detectors are often not truly
  ubiquitous

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Goals

• SPEEDY
• integrated in a wrist watch
• easy to handle (one button)
• innovative algorithm basedon acceleration
  sensing
• simple and low power

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Concept

• Two sensors (ADXL202) with two axes each measure
  the static acceleration of the device(1g 9.81
  ms-2 in standstill)
• There are six degrees of freedom for the arm
  movement
• no knowledge of the devices bearing or
  orientation
• We work with the Norm
• independent of bearing

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Principle of Detection

• Monitor the wearers speed relative to the ground
• how detect the speed relative to the ground when
  the orientation of the device is unknown?

-2
9.81ms
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Principle of Detection

• Monitor the wearers speed relative to the ground
• how detect the speed relative to the ground when
  the orientation of the device is unknown?
• The vertical speed is estimated by a rough
  approximation
• only little computing power is needed

-2
9.81ms
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Principle of Detection (2)

• the approximation is fundamentally wrong for high
  accelerations towards the ground ( )

-2
9.81ms
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Principle of Detection (2)

• the approximation is fundamentally wrong for high
  accelerations towards the ground ( )
• Integrating the approximation yields to different
  inaccuracies
• norm and integral are not commutative
• offset and noiseof the ADXL202

-2
9.81ms
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Principle of Operation

• Measuring theorientation
• ADXL202
• User Interface
• input
• 1 button
• output
• LED
• buzzer

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Principle of Operation

• Measuring theorientation
• ADXL202
• User Interface
• input
• 1 button
• output
• LED
• buzzer

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Principle of Operation

• Measuring theorientation
• ADXL202
• User Interface
• input
• 1 button
• output
• LED
• buzzer

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Visualization on the computer

• wireless transmissionof the measurement data

• calibrationof the sensors

emulation of the data analysis algorithms
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Results

• Recording duringa fast fall
• detection of thefall is based on
• 1) high velocity
• towards the
• ground
• 2) impact
• 3) inactivity

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Results (2)

• Recording during a strong handshake
• no detection offall (phase 1)because of speed2

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Results (3)

• The success story
• only 65 of possible dangerous falls
  weredetected
• no false alarmduring a two-daytrial in real life

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Conclusions

• We developed a fall detector in the form of a
  wrist watch.
• truly ubiquitous
• no false alarm
• high acceptance for the elderly
• The device is best fitted for practical tests in
  social housing
• data logging
• wireless transmission
• software analysis tool

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Conclusions (2)

• Yet, the device is not ready
• detection rate only 65
• power consumption too high (2.6 mA)

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Demonstration
acceleration values
subject (m 33y)
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Outlook

• Using low-power acceleration sensors
• Adding a pressure sensor device
• Incorporating a small loop antenna

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Outlook (2)

• Antenna gain and orientation

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Outlook (3)

• New algorithm for velocity towards the ground
• no approximation
• low computational power

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SPEEDY A Fall Detector in a Wrist Watch
Thank you for your attention.
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Hardwareplatform

• MSP430F149 Controller
• 2 Accelerometer ADXL202 (2g), 3 Raumachsen
• Serielle Schnittstelle, Taste, Beeper, Led
• Batteriebetrieb ca. 2 Wochen
• Daten-Logging 40s (Flash)
• Mit Wireless-Modul

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Demonstration
Nur Fall (Speed1) und Aufschlagsdetektion

• Ruhezustand Led blinkt langsam (1Hz)
• Erschütterung
• Fall Led blinkt schnell (5Hz)
• Fall und Erschütterung - Sirene heult

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Demonstration
Nur Fall (Speed1) und Aufschlagsdetektion

• Vorgeschichte unnötige Todesfälle alter
  alleinlebender Personen (Oberschenkhalsbruch,
  Fettembolie)
• GSM, (GPS) für Positionsangabe, Rettungseinsatz