Detection of Patient Falls Using Three-Axis Accelerometer Umer Jamshaid Tyler Quarles Parampal Randhawa Martha Serna Matthew Treinish April 26, 2011 School of Electrical and Computer Engineering

2 One in three people over 65 fall each year, and more than 300,000 hip fractures occur each year because of falls* Broken Hipsters Monitoring System (BHMS) o What: Creation of automated fall detection system o Why: Large number of fall related injuries o Who: Residents at Assisted Living Centers o Cost: $59 per unit Project Motivation 1

3 Design Goals: Proposed vs Achieved Fall Detector  Small enough to wear  Low cost  Low power  Detects different falls Control Box  Detect resident in bed with pressure sensors  Send alert signal to caretaker’s station Fall Detector  Prototype designed that can be scaled down  Cost at $59  Low power: 40mA, enough for 5.6 hours of continuous use  Detects orientation vs acceleration  Control Box  Correctly detect resident in bed with pressure pad  Send alert signal to caretaker’s station 2

4 BHMS Design Overview PIC18 Microprocessor Pressure Pad Red LED Three-Axis Accelerometer Xbee Module PIC18 Microprocessor Orientation Data Xbee Module Fall Detector Control Box Wireless Communication Pressure Data Alert Signal 3

5 Fall Detector – PCB & Protoboard 4

6 Control Box – Protoboard Enclosure 5

7 Fall Detector Design Details Analog three-axis accelerometer –Only used readings from one axis Threshold angle 35 degrees from horizontal –Detects falls in all directions (including inverted!) Detection loop runs for 18 seconds XBees communicate in Transparent Mode Protoboard runs off 3.3 V power supply –PCB designed to run off 3 V coin cell battery 6

8 Control Box Design Details Pressure pad used with ADC to prevent false positives LED lights up to represent Alert Signal Clear button to reset Fall Detector algorithm Control Box plugs into power socket –Voltage regulator on board converts to 3.3 V 7

9 BHMS Design Testing Used XBee Explorer with X-CTU to monitor and simulate wireless communication Tested possible fall scenarios with programmed Fall Detector and Control Box Used acknowledge signals from Control Box to ensure reliable communication Tested Fall Detector range in lab (10 m) XBees rated to 30 m indoors 8

10 Room Layout Resident with Fall Detector Control Box Pressure strip 9

11 Fall Detection Algorithm 10

12 Design Issues Switched to analog accelerometer XBee reset –Unable to control, disconnected XBee configuration Clear button –Required to press multiple times Accelerometer data –Peaks when flat –Fixed by adding high and low threshold values 11

13 BHMS Design Specifications Detect different types of falls, within 30 s (Y) Pressure sensor on bed filters out false positives Small size, lightweight (Y) Fall Detector able to fit onto 2.5 in 2 PCB Range of 20 m Tested to 10 m Battery life of 1 month (N) Current code only lasts 5 hours on 3 V coin cell Sleep mode for XBees can improve battery life 12

14 Final Budget Analysis Cost of Materials: $1, Cost of Labor: $18, o Cost of labor is based on 5 entry level engineers Prototyping first product will be expensive o Total cost: $ 20, Mass production will lower the cost of product. o Final cost after 1000 units sold: $

15 Potential Future Work Add touch screen GUI at caretaker station Decrease battery consumption by sleeping the XBees when not in used Implementing a multi-room solution using the networking features of the XBees Include sitting falls in detection algorithm Expand BHMS using modular design 14

16 Questions? 15