A MYOELECTRIC HAND PROSTHESIS FOR WRITING ENGLISH ALPHABETS

Ashish SundarCo author: P. Prema (Senior Assistant Prof.)

School of Bio-Sciences and TechnologyVIT University, Vellore

Tamil NaduIndia

CEMI-2010, CSIO, Chandigarh

Overview:Overview:

To develop: Low cost prosthetic hand Capable of writing English alphabets with a pen Sensing the EMG of identified, available arm muscles Work done for writing four letters, “L”, “I”, “V” and “E”

CEMI-2010, CSIO, Chandigarh 2

Source: http://www.shadowrobot.com

Block Diagram:Block Diagram:

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Sections:Sections:

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(circuit dia.)

(circuit dia.)

(filter chara.)

(EMG chara.)

(results)

Microcontroller section:Microcontroller section:

5VIT University, April 2010

Servo working:Servo working:

6

0.5 ms pulse train – rotate the shaft anticlockwise, -90 degrees

1 ms pulse train – fixes the shaft at 0 degrees

1.5 ms pulse train – rotate the shaft clockwise, +90 degrees

CEMI-2010, CSIO, Chandigarh

Design of the Hand:Design of the Hand:

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(DOF)

(design)

Character segmentation:Character segmentation:

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(flow chart)

The Letters ….>The Letters ….>

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The whole setup The whole setup

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Conclusion:Conclusion:

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A five fingered spring loaded tendon driven hand prosthesis was developed.

The hand which was developed with low cost materials and reliable methods has shown satisfactory results.The current design can undergo further design modifications and can be made into much more sophisticated model in all aspects. With the addition of more number of motors and tendons the functionality of the whole system can be increased by increasing the number of active motions. The EMG circuitry which shown less noise immunity, can be made more immune with the use of proper shielding wires and proper electrodes

References:References:

Mechatronic Experiments Course Design: A Myoelectric Controlled Partial-Hand Prosthesis Project; Ton-Tai Pan, Ping-Lin Fan, Huihua Kenny Chiang, Member, IEEE, Rong-Seng Chang, and Joe-Air Jiang, Member, IEEE; IEEE TRANSACTIONS ON EDUCATION, VOL. 47, NO. 3, AUGUST 2004

Algorithm for Robot Writing using Character Segmentation: Salman Yussof, Adzly Anuar, Karina Fernandez, Universiti Tenaga Nasional Jalan Kajang-Puchong 43009 Kajang, Selangor, Malaysia; PROCEEDINGS OF THE THIRD INTERNATIONAL CONFERENCE ON INFORMATION TECHNOLOGY AND APPLICATIONS (ICITA’05) 0-7695-2316-1/05

Digital Butterworth filter for subtracting noise from low magnitude surface electromyogram: Roger G.T. Melloa, Liliam F. Oliveirab, Jurandir Nadal; ELSAVIER: COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 87 (2007) 28–35

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THANK YOU….THANK YOU….

CEMI-2010, CSIO, Chandigarh (title)

EMG characteristics :EMG characteristics :

CEMI-2010, CSIO, Chandigarh

•An extracellular field •Generated when the muscle fibers extend along the length of the muscle •Duration of 3- 15 ms•Amplitude ranges from 20 – 2000 microV•Recorded using bipolar electrodes

(back)

Bessel’s Filter chara:Bessel’s Filter chara:

CEMI-2010, CSIO, Chandigarh

(back)

EMG circuit diagram :EMG circuit diagram :

CEMI-2010, CSIO, Chandigarh

• Fourth order Bessel’s filter

Design of HPF FC = fn / (2πRC)

Design of LPF FC = 1 / (2π fn RC)

Butterworth Bessel Chebyshev (0.5 dB)

K(gain) Fn K(gain) Fn K(gain)

2 1.586 1.272 1.268 1.231 1.842

4 1.1522.235

1.4321.606

1.0841.759

0.5971.031

1.5822.660

61.0681.5862.483

1.6071.6921.908

1.0401.3642.023

0.3960.7681.011

1.5372.4482.846

(back)

Detector section:Detector section:•Voltage threshold of 1V was given

• Pulses equivalent to Vcc is produced when input crosses the limit

DesignV1 = (VCC x R2) / (R1 + R2)

CEMI-2010, CSIO, Chandigarh (back)

Algorithm of program:Algorithm of program:Micro controller runs in two modes:

•Time delay mode •To check ports

•Interrupt sub-routine•To reset the motors to the starting position

CEMI-2010, CSIO, Chandigarh

(back)

As DOF increases, the complexity also increases Complexity increased by increase in the number of actuators

Single DOF robotic hands are also available

CEMI-2010, CSIO, Chandigarh

Source: http://www.shadowrobot.com

Robot hand

BH8-series Barrett hand

Barrett technology,

inc. USA

DIST HandUniversita di Genova

Italy

Robonaut HandNASA

Johnson Space Center

USA

DLR Hand II

DLR-German

Aerospace Center

Germany

Ultralight Hand

Research center of

KarlsruheGermany

GIFU HandGifu

UniversityJapan

Shadow Hand

Shadow Robot

Company Ltd

United-Kingdom

UB Hand III

Bologna University

Italy

Structures and materials

3 fingers (opposable),Electrical revolute brushless motors,Spur and worm gear transmissionFair contact surface smoothness

3 fingers and one opposable thumb,Electrical revolute brushless motors,Tendons routed through pulleys

4 fingers and one opposable thumb,Electrical revolute brushless motors,Flex-shaft + lead screw transmissionKevlar body armor coated with Teflon

4 fingers and one opposable thumb, Electrical revolute motors,Harmonic drives/gears transmissionSilicone finger surface

4 fingers and one opposable thumb,Flexible fluidic actuators,Direct drive transmissionSilicone-rubber glove

4 fingers and one opposable thumb,Built-in DC Maxon servomotorsWorm gear transmissions

4 fingers and one opposable thumb,Air Muscles,Tendons,Layer of soft polyurethane flesh, Thin polycarbonate fingernails

4 fingers and one opposable thumb,DC brushed motor,Pulling tendons,Continuous compliant pulps

CEMI-2010, CSIO, Chandigarh

Source: http://www.shadowrobot.com

(back)

Design of the Hand:Design of the Hand:

CEMI-2010, CSIO, Chandigarh

•Spring loaded hinge mechanism •Integrated distal and middle phalanges•Thickness of 0.6mm for spring element[1] and 0.8mm for spring element [2]•PIP joint of forefinger activates y axis motion•MCP joint of thumb activates x axis motion

• Five fingered hand with 2 DOF•Tendon driven mechanism• Has mainly two types of motion:

•Active and•Passive

•Made from cheap materials• Provision for increasing the DOF•Can be used as an universal hand

CEMI-2010, CSIO, Chandigarh (back)

Filter response:Filter response:• Response of filter + instrumentation amplifier• Found to be satisfactory• The cut- off can be increased with the usage of higher order filters• A cut off of 50 Hz for high pass filter• A cut off of 500 Hz for low pass filter

CEMI-2010, CSIO, Chandigarh

EMG obtained:EMG obtained:

…Noisy signals…

•EMG can always be affected by noise• Proper insulation or noise reducing cables should be used

CEMI-2010, CSIO, Chandigarh

Detector section:Detector section:

•Voltage detector output is seen as pulses

• These pulses will be driving microcontroller

CEMI-2010, CSIO, Chandigarh

(back)