1. Analysis of Gait Patterns by Using a Sound Sensor and Wireless Communication Miku Teruya Department of Information Communication, Okinawa National College of Technology, Okinawa, Japan

2. Content Introduction Measurement Process of Gait Patterns Analysis of Sound and Vibration from Footsteps Classification of Gait Pattern Wireless Measurements of Sounds Conclusion

3. Introduction Gait pattern has so far been studied on strides and foot steps Past analysis method Aim of our research Study on distinguishability of a person by classifying waveforms of sounds generated by foot steps Issues Motion Capture Foot Pressure Expensive instruments High volume data processing Distinguishable for visible person only

4. Sounds Generated by Footsteps Animals such as cats, dogs, and rabbits can distinguish its owner by hearing sounds generated by footsteps We focused on analyzing waveforms of sounds generated by footsteps

5. We used ECM (Electret Condenser Microphone) as a sensor for measurements of sounds. Configuration of Sound Sensor

6. Design of Transistor Amplifier Design with variable gain for specific frequency by manually adjusting the circuit parameters during the measurements. To ECM R11 R13R12 R10 R2 R8 To oscilloscope Transistor Amplifier Variable Resistors

7. Adjustment of Circuit Parameters for Optimization of Amplifier Gain R11 =1.5k [Ω] 6k [Ω] R12 =60 [Ω] 0 [Ω] R13=0 [Ω] 120 [Ω] R11=500 4.5k[Ω] R13=0 120[Ω] R12=0 120[Ω] Adjustable R13 for over all gain Frequency (Hz) Gain(dB) Frequency (Hz) Gain(dB) Adjustable R12 for gain at lower frequency Adjustable R11 for SN optimization 500 [Ω] 120 [Ω]

8. Measurements Process of Gait Patterns Measurements Different Gait Patterns for Stride: wide /small Scrape step, Toe landing, Heel landing Measured for eleven different people Sounds collector plate Condenser microphone Transistor amplifier Portable Oscilloscope Computer Measured data Analyzed data

9. Analysis of Sounds and Vibration Analysis of measured waveforms; Classified with Wave Number, Wave Width,Wave Interval Wave number Wave width Wave interval Wave Number Wave Width[ms] Wave Interval[ms] H J Subject HSubject J Comparison between two people of H and J Time[ms] Voltage[V] Time[ms] Wave width Wave number Wave interval

10. Analysis by Wave Number Large Stride : Wave number is less than 4 Small Stride : Wave number is higher than 6 Red Circles shows each person Stride: small Stride: Large Wave Number Wave number : less than 4 Voltage[V] Time[ms] Wave number : higher than 6

11. Analysis by Wave Width and Interval Heel landing Wave width less than 230ms Toe landing Wave width between 230 and 290ms Scrape steps Wave width higher than 290ms & Wave interval less than 360ms Wave WidthWave Interval Red circles show each person Heel Landing Toe Landing Scrape Steps Wave width:150 230ms Wave width 230 290ms Wave width higher than 290ms Wave Interval less than 360ms

12. Step Speed Wave width Wave Interval Wave width + Wave interval = One Step[s] Numbers of steps per minute =60[s]/(Wave width + Wave interval)[s] Low step speed : less than100[step/min.] High step speed : higher than 110[step/min.] Step Speed Time[ms] Voltage[V] Wave width +Wave interval Red circles show each person

13. Verification of Repeatability Subject B Subject F Wave forms were measured 4 times for two people of B and F 1st2nd 3rd 4th 1st2nd 3rd 4th

14. Comparison and Classification of Waveforms Feature of waveforms measured for four people Step speed [step/min]

15. Two Types of Sound Measurement Methods ItemWiredWireless Measurement Distance Less than 3mLess than 1km Sound SensorEmbedded in floorAttached to shoes EquipmentSimple configurationComplicated configuration Floor MaterialLimited selectionEasy to choose Type of Shoes Free selection Fixed SoundMainly generated by vibration of the floor Mainly generated by mechanical shock of the shoes landing

16. Wireless Transmitter and Receiver Receiver antenna Shoes with ECM Portable Oscilloscope 2.4GHz Wireless receiver 2.4GHz Wireless transmitte r Video capture Amplifier circuit Video Camera Transmitter antenna Computer for observation

17. Measurements of Waveforms with Wireless Communication The sound signals were transmitted by 2.4GHz wireless transmitter Sound voltage signals were generated at the ECM attached outside of the shoes The signals were received by 2.4GHz wireless receiver The sound data analysis were carried out by an Excel Macro Software

18. Waveforms from Right and Left Feet Right foot Left foot Right foot Left foot Amplitude [V] Transmitted by two channels of wireless frequencies

19. Comparison and Classification of Waveforms with Different Floor Materials Right foot Left foot

20. Application of Gait Pattern Analysis Investigation of Status of Human Body Detects the condition of health from the state of the gait pattern. Applicable to medical care and health. Security System Applicable to security to admit authorized personnel into protected house and building. Sensor of Engine Sound Applicable to warning system for electric vehicles. Waveform generated by a vehicle

21. Conclusion We classified the waveforms with 4 factors of wave width, wave interval, and step speed by analyzing the sound generated by foot steps. We distinguished the gait patterns of eleven people by using the 4 factors. We remotely measured sounds generated by a walking person in the distance by using 2.4GHz wireless communication. We classified the waveforms according to different floor materials. Our analysis procedure would be useful for detecting the status of health and the security system.