Analysis of Gait Patterns by Using a Sound Sensor and Wireless Communication

Miku TeruyaDepartment of Information Communication, Okinawa National College of Technology,Okinawa, Japan

Content

Introduction Measurement Process of Gait Patterns Analysis of Sound and Vibration from

Footsteps Classification of Gait Pattern Wireless Measurements of Sounds Conclusion

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

　

IssuesMotion Capture 　Foot Pressure 　　　　　　　

Expensive instruments High volume data processing Distinguishable for visible person only

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

　

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

Configuration of Sound Sensor

Design of Transistor Amplifier

Design with variable gain for specific frequency by manually adjusting the circuit parameters during the measurements.

To ECM

R11

R13 R12R10

R2R8 To oscilloscope

Transistor Amplifier

Transistor Amplifier

Variable Resistors

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)

　G

ain(

dB)

　G

ain(

dB)

　 Frequency 　(Hz)

　 Frequency 　(Hz)

　G

ain(

dB)

Adjustable R12 for gain at lower frequencyAdjustable R11 for SN optimization

500[Ω]120[Ω]

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

Condensermicrophone

Transistoramplifier

Portable Oscilloscope

Computer

Measured data

Analyzed data

Analysis of Sounds and Vibration Analysis of measured waveforms;　 Classified with ①Wave Number, ②Wave Width,③Wave

Interval　　　　　　　　　

　

①Wave number

②Wave width

③Wave interval

①Wave Number

②Wave Width[ms]

　

③Wave Interval[ms]

H ５ １５２．７ ４５９．６J ３ ３３８．５ ３６０．４

Subject H Subject J

Comparison between two people of H and J

Time[ms]

Volta

ge[V

]

Volta

ge[V

]Time[ms]

②Wave width

①Wave number

③Wave interval

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: smallStride: LargeWave Number

Wave number : less than 4

Volta

ge[V

]

Volta

ge[V

]

Time[ms] Time[ms]

Wave number : higher than 6

Analysis by Wave Width and Interval

　　　　　　　　　　　　　　　

Heel landing ： Wave width less than 230msToe landing ： Wave width between 230 and 290ms Scrape steps ： Wave width higher than 290ms & Wave interval less than 360ms

Wave Width Wave Interval

※Red circles show each person

Heel Landing Toe Landing Scrape Steps

Wave width:150～ 230msWave width： 230～290ms　

Wave width： higher than 290ms

Wave Interval： less than 360ms

Step Speed

②Wave width ③Wave 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]

Volta

ge[V

]

②Wave width +③Wave interval

※Red circles show each person

Verification of Repeatability

Subject B

Subject F

Wave forms were measured 4 times for two people of B and F

1st 2nd 3rd 4th

1st 2nd 3rd 4th

Comparison and Classification of Waveforms

Feature of waveforms measured for four people

Step speed [step/min]

Two Types of Sound Measurement Methods

Item Wired WirelessMeasurement Distance

Less than 3m Less than 1km

Sound Sensor Embedded in floor Attached to shoes

Equipment Simple configuration Complicated configuration

Floor Material Limited selection Easy to chooseType of Shoes Free selection Fixed Sound Mainly generated by

vibration of the floor

Mainly generated by mechanical shock of the shoes landing

Wireless Transmitter and Receiver

Receiver antenna

Shoes with ECM

Portable Oscilloscope

2.4GHzWireless receiver

2.4GHzWireless transmitter

Video capture

Amplifier circuit

Video Camera

Transmitter antenna

Computer for observation

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

Waveforms from Right and Left Feet

Right foot

Left foot

Right footLeft foot

Ampl

itude

[V]

Transmitted by two channels of wireless frequencies

Comparison and Classification of Waveforms with Different Floor Materials

Right footLeft foot

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

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.