Development of a Smart Walking Cane with Biofeedback I S A B E L L E D . P U M F O R D 1 , 2 , M A R C U S J . B A I L E Y 1 , 4 A N D P A T R I C K M . A U B I N 1 , 3 , 1 R R & D C E N T E R O F E X C E L L E N C E , V A P U G E T S O U N D , S E A T T L E , W A , 2 C O L L E G E O F E N G I N E E R I N G A T U N I V E R S I T Y O F A R K A N S A S , F A Y E T T E V I L L E , A R 3 D E P A R T M E N T O F M E C H A N I C A L E N G I N E E R I N G A N D S C H O O L O F M E D I C I N E 4 , U N I V E R S I T Y O F W A S H I N G T O N , S E A T T L E , W A E M A I L : I D P U M F O R @ U A R K . E D U
Introduction 27 million adults suffer from Osteoarthritis in the United States Reducing knee adduction moment, KAM, has been show to decrease pain and improve function Wanted to create a walking aid that encourages increased cane loading and KAM reduction using a vibrotactile biofeedback loop
Device Requirements Provide cane load biofeedback Mobile battery operated Able to store data Person up to 113 kg (250 lbs) Able to measure force from 0N to 222N Able to record date and time Similar weight to conventional cane. Able to mechanically withstand up to 222N
Initial Design Force Link outputs charged based on piezoelectric effect. Displacement results in a charge being created. When compressed an Inline Amplifier creates a charge from 0-5V; can detect up to 265N. Force Link Handle holding electronics bent during testing
Current Design 6mm motor Smart Cane provides biofeedback in the form of a vibration when 20% of user’s body weight is loaded On and off switch PBC protects components and allows for sturdy exterior
Electronics Real Time Clock (RTC) Open logger for SD card Motor Controller Promicro Controller • Promicro controls computerized system Open logger allows data to be stored on SD card • • Real Time Clock records actual time and date for record keeping • Motor controller controls vibrating motor
Electronic Communication Inter-Integrated Circuit (I 2 C) Pulse Width Modulation (PWM) RTC Motor Controller TX ProMicro RX Serial Link 10bit Resolution Analog Pin SD Logger Inline Amp
Force Measurement Validation Force Measured by Cane and Force Plate 0 0 100 200 300 400 500 600 -20 -40 Force (N) -60 -80 Cane -100 Force Plate -120 -140 -160 -180 Sample Number (time) RMS Error ±2.5 N
Arduino Software Records force Records peaks Turns motor on and off Loop repeats every 20 milliseconds, 50 hertz Peak Max threshold Force (N) Min threshold Time
Conclusion Requirement Smart Cane Provide cane load biofeedback Vibrotactile feedback loop Mobile battery operated Untethered and uses Li-ion batteries Able to store data Data logger uses SD card Person up to 113 kg (250 lbs) Yes Able to measure force from 0N to 222N Up to 265N Able to record date and time Uses RTC for real time and date Similar weight to conventional cane. About 2 kg of weight added Able to mechanically withstand up to New PBC model is able 222N
Acknowledgements and Questions Study funded by the Department of Veterans Affairs grant A9243C; RR&D Center of Excellence for Limb Loss Prevention and Prosthetic Engineering., VA Puget Sound, Seattle WA.
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