Directional vs Non-directional Modes of Vibrotactile Feedback for Arm Posture Replication

Albert Causo, Le Dung Tran, Song Huat Yeo and I-Ming Chen

School of Mechanical and Aerospace Engineering

Nanyang Technological University, Singapore

25th

Jun 2012

1

Motivation & Objective http

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15m

67%

stroke patient

survive

Develop low-cost device

for rehabilitation

Best feedback strategy for

posture correction2

Presentation Outline

System Overview

Arm Posture Modeling & Measurement

Vibo-tactile for Posture Correction

3

Different ways of capturing motion

Inertial Motion Unit

MAGNETIC

MECHANICAL

SYSTEM

OPTIC

System Overview Modeling Vibro-tactile

4

Vibro-tactile Feedback

posture guidance

motor learning hand

rehabilitation

5

System Overview Modeling Vibro-tactile

IMU

IMU

Vibro-tactile Unit

System Overview

IMU

Vibro-tactile

Unit

6

System Overview Modeling Vibro-tactile

Software

Arm Posture Modeling

Wrist

Position

Elbow

Position

Forearm

Roll

7

System Overview Modeling Vibro-tactile

Shoulder

Wrist

Elbow

IMU 1

IMU 2

𝐿2

𝐿1

Arm Posture Kinematics

IMU 1 -

𝑟1 ,𝑝1 , 𝑦1

IMU 2 -

𝑟2 ,𝑝2 , 𝑦 2

Arm Lengths -

𝐿1,𝐿2

𝑓 (𝑟 1 ,𝑝1 , 𝑦 1 ,𝑟2 ,𝑝2 , 𝑦 2 ,𝐿1 ,𝐿2)𝑓 (𝑟 2 ,𝑝2 , 𝑦2 ,𝐿2)

wrist -

elbow -

forearm roll -

𝑟1

8

System Overview Modeling Vibro-tactile

Vibro-tactile feedback for arm posture correction

Vibro-tactile unit

Directional feedback

Non-directional feedback

9

System Overview Modeling Vibro-tactile

Directional Feedback Non-directional Feedback

Global

system at

shoulder 10

right hand right hand

System Overview Modeling Vibro-tactile

Local

system at

wrist

Experiments

1 2 3

4 5

11

System Overview Modeling Vibro-tactile

Calibration Step

12

System Overview Modeling Vibro-tactile

Using Vibro-tactile Feedback

Directional Feedback Non-directional Feedback

1m36s 25s13

System Overview Modeling Vibro-tactile

Results

Feedback Strategy Mapping Time (s)Directional Feedback 52.68 ± 17.98

Non-directional Feedback 36.82 ± 19.37

2 3

1 42 3 5

Average error of 7 subjects for 5 posturesAverage error of 7 subjects for 5 postures

14

The use of tactors as directional & non-directional feedback

Error Directional Feedback Non-directional Feedback

Wrist position (mm)

34.42 ± 22.46 26.61 ± 12.92

Elbow position (mm)

20.63 ± 9.53 19.61 ± 9.56

Forearm roll (deg) 6.81 ± 2.96 7.07 ± 3.05

System Overview Modeling Vibro-tactile

Conclusion

IMU

IMU

Vibro-tactile Unit

Integrated System

Arm Posture Modeling

& Measurement

Vibo-tactile for

Posture Correction

15

Future Work

• Combine active visual + audio + vibro-tactile feedback

• Compare direction & non-direction when adding vision

• Design rehab modules

16

Thank you!

Email: tran0055@e.ntu.edu.sg

17

APPENDICES

18

Design of GUI

Experiment tabTesting tabConfiguration tab 19

Software - System Overview

StartReceive

Master’s IMU

data

Determine

target

position

Receive

Student’s

IMU data

Determine

current

position

Handle

error

Send tactile

feedbackFinish

Student

adjusts

his/her arm

+-

Arm Replication Process

IMU Measurements

IMU packs 9 sensors (3 accelerometers, 3 angular rate

gyros, 3 magnetometers)

Given the angular value at (t − 1) and t, the numerical approximation becomes

Inertial Motion Unit

Kinematic Formulation (1)

Cartesian transformation

Kinematic Formulation (2)

Yaw - z axis

Pitch - y axis

Roll - x axis

Kinematic Formulation (3)

IMU Specification

Tactor Specification

Specifications of VPM2

VPM2 tactor

Dimensions of VPM2

Capture of Program

IMU device

Vibrotactile Unit

Average error of 7 subjects for 5 posturesAverage error of 7 subjects for 5 postures

Data

Directional and non-directional feedback indicators

Feedback Strategy Mapping Time (s)

Directional feedback 52.68 ± 17.98

Non-directional feedback 36.82 ± 19.37

Average mapping time of 7 subjects for 5 posturesAverage mapping time of 7 subjects for 5 postures

Error Directional feedback Non-directional feedback

Wrist position (mm)

34.42 ± 22.46 26.61 ± 12.92

Elbow position (mm)

20.63 ± 9.53 19.61 ± 9.56

Forearm roll (deg) 6.81 ± 2.96 7.07 ± 3.05

Threshold values

Directional and non-directional experiments