A Human Fall Detection System:

Transcription

1 A Human Fall Detection System: Using leading edge technology Sensor and Analog Product Division RTAC Americas

2 Human Fall Detection System The problem How to detect the fall of a person in different situations? A person's fall is usually an indicator of an emergency, especially in some groups (elderly people, firemen, policemen). Using Freescale cutting edge technology (Triaxial Accelerometer, DSC and RF Transceiver), a person's fall can be detected and reported for immediate response. This paper presents an approach taken to solve the "human's fall" problem as well as the Hardware and Software required to perform the implementation of such approach. Slide 1

3 What is known about the Human Fall problem? Several studies have been made for systems that monitor human activities Accelerometers Labeled Water Calorimeters Advantages of Accelerometers > They are small and can be mounted easily on the body > Can be easily interfaced with a portable processing unit > They are low power sensors Determining Activity Using a Triaxial Accelerometer 2002 A Triaxial Accelerometer and Portable Data Processing Unit for the Assessment of Daily Physical Activity 1997 Detection of Static and Dynamic Activities Using Uniaxial Accelerometers 1996 Activity Monitoring with accelerometry 1994 Exploring the information content and some applications of body mounted piezo-resistive accelerometers 1994 Accelerometry A technique for the measurement of human body movements Slide 2

4 Requirements of the System It is small can be easily attached to the person It is battery powered It detects a person s fall with good accuracy When a Fall is detected, the event is reported to a station and saved into a Non-Volatile memory in the device The device can receive and execute commands from the Station to control the Non-Volatile memory Slide 3

5 Hardware Architecture Hardware Slide 4

6 Hardware Architecture 9V BATT Volt reg. Antenna Serial communications Interface (RS-232) 2 LEDs, 1 Buzzer, 2 Push-Buttons Processing Unit RF Xcvr Matching Network JTAG Interface FILTER G Select XYZ Accelerometer Slide 5

7 The Triaxial Accelerometer MMA7260Q High Sensitivity Power Save Mode: 5 µa Low Noise Low Power 2.2 V to 3.6 V Operation 6mm x 6mm x 1.45 mm QFN Integral Signal Conditioning with Low Pass Filter Linear Output Ratiometric Performance Robust Design, High Shocks Survivability Triaxial Accelerometer Hardware Slide 6

8 Triaxial Accelerometer s role Hardware The Accelerometer gives three signals corresponding to the sensed acceleration in each axis. The two lines for G-selection are controlled directly by the MCU. The power save pin is connected to Vdd to allow the Accelerometer to be on constantly. Slide 7

9 Digital Signal Controller MC56F MIPS at 32MHz core frequency Single-cycle bit parallel MAC Four 36-bit accumulators DSP and controller Instruction set Efficient C compiler and local variable support JTAG/EOnCE debug programming interface 16KB of Program Flash 4KB of Unified Data/Program RAM One six-input, 12-bit, Analog-to-Digital Converter (ADC), One Serial Communication Interface (SCI) with LIN Slave functionality One Serial Peripheral Interface (SPI) Slide 8 Processing Unit Hardware

10 Digital Signal Controller MC56F MIPS at 32MHz core frequency Single-cycle bit parallel MAC Four 36-bit accumulators DSP and controller Instruction set Efficient C compiler and local variable support JTAG/EOnCE debug programming interface 16KB of Program Flash 4KB of Unified Data/Program RAM One six-input, 12-bit, Analog-to-Digital Converter (ADC), One Serial Communication Interface (SCI) with LIN Slave functionality One Serial Peripheral Interface (SPI) Slide 9 Processing Unit Hardware

11 Digital Signal Controller s role Hardware The DSC controls the behavior of the Accelerometer, the User controls and indicators, the I2C memory and the RF Transceiver. It process the Accelerometer outputs to generate information about the Human state, and to determine whether he or she has fallen or not. Slide 10

12 RF Transceiver Hardware RF Transceiver MC13192 Compatible with IEEE Standard Power supply range: 2.0 to 3.4 V 16 RF Channels 0 dbm nominal, programmable up to 4 dbm typical maximum output power Buffered transmit and receive data packets for simplified use with low cost MCUs Three power down modes for power conservation Programmable frequency clock output for use by MCU Onboard trim capability for 16 MHz crystal reference oscillator Small form factor QFN-32 Package Slide 11

13 RF Transceiver s role Hardware The RF Transceiver gives the system the capability to report an event or emergency to a base station. It is also the way to access the data on the I2C Memory. The protocol used to transmit the Data was created over a modified version of SMAC4.1. Slide 12

14 Software Architecture Software Slide 13

15 Software Architecture Slide 14

16 Foreground Details - Software AS_INIT: Initialization of the System AS_IDLE: All the user level functionality is provided AS_DATAPROCESSING: The Data Processing state machine is started. AS_HUMANSTATE: Computes the Human state and responds to it. Slide 15

17 Data Processing Foreground Details - Software DP_INIT: Initialization of Buffers DP_HPFILTER: Perform the FIRs needed DP_ENERGYDETECT: Computation of the Energy Expenditure (for 0.8 s) DP_OUTPUTCONDITIONING: Computes the Human state and responds to it. DP_DEBUG: If active, the debugging mode is performed here. DP_PROCESSFINISH: Prepare the next iteration and return to main. Slide 16

18 Example Example of the Data Processing Slide 17

19 Example of the Data Processing Sample Frequency: 45 Hz Median Filter Length: 13 samples FIR Filter window length: 36 samples (0.8 sec) (non overlapping) Slide 18

20 Input Signal - Example of the Data Processing g - m/s2 0 X Y Z time - sec Slide 19

21 Median Filter - Example of the Data Processing g - m/s2 0 X Y Z time - sec Slide 20

22 High Pass Filter - Example of the Data Processing g - m/s2 0 X Y Z time - sec Slide 21

23 Energy Detection - Example of the Data Processing X g - m/s Y Z Energy time - sec Slide 22

24 Software Tools Processor Expert Processor Expert Is an Object-oriented, application development tool that reduce your time to market Functionality is defined by properties, methods, events Software and peripheral beans are hardware independent Hardware independence and inheritance make applications portable CPU dependent settings are checked against the knowledgebase Beans are ready-to-use, tested components with complete documentation Process Expert generates highly optimized code Slide 23

25 Software Tools Processor Expert Slide 24

26 Slide 25 Software Tools Simple MAC Simple Media Access Controller (Simple MAC) Compact footprint: 2K FLASH 10 bytes (+ maximum packet length) RAM As low as 16kHz bus clock Can be used to demonstrate coin cell operation for a remote control MC1319(1, 2, 3) compatible Very-low power, proprietary, bi-directional RF communication link ANSI C source code targeted for the HCS08 core and ported to almost any CPU core (including 4-bit) Low priority IRQ Sample application included. Easy to use Liberally commented

27 Experiments Definition Results The experiments were defined as follows: - 10 men were selected (ages from 22-30) and were required to perform several sequence of movements three times each. - A device was attached to their belt (in the low back) holding a prototype of this system board. No computation was made, it only transmitted the accelerometers data through the air (using the ZigBee transceiver) and gathered in a PC. Slide 26

28 The specific sequence of movements were: Experiments Definition Results Standing Fall Normal Walk And Fall Going Upstairs Normally Going Downstairs Normally Going Upstairs Fast Going Downstairs Fast Drunk Walk and fall Running Jogging Jumping Running and jump Jogging and jump Walk-Crouch-Stand Walk-Crouch-Walk Stand-Crouch-Stand Laying-Slowly stand up Laying-fast stand up Laying, compulsion simulated Elevator going up Elevator going down Laying, no movements Slide 27

29 Example of Energy Level per Activity - Results Human activity clasification 10 1 Average EE 0.1 Fall Lying Standing Transition Walking Standard Deviation EE Slide 28

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