Transcript op1.1 - csio

A MYOELECTRIC HAND PROSTHESIS FOR
WRITING ENGLISH ALPHABETS
Ashish Sundar
Co author: P. Prema (Senior Assistant Prof.)
School of Bio-Sciences and Technology
VIT University, Vellore
Tamil Nadu
India
CEMI-2010, CSIO, Chandigarh
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”
Source: http://www.shadowrobot.com
CEMI-2010, CSIO, Chandigarh
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Block Diagram:
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Sections:
Instrumentation
Amplifier
• INA 118P was used for its high CMRR and
compactness
• Used a Gain of 250
• High noise immunity
(EMG chara.)
Bessel’s Filter
• Fourth order band pass filter
• Selected for its linear phase- freq. response
• Cut off of 50Hz for HPF and 500Hz for LPF
(filter chara.)
Voltage detector and
End stage Amplifier
(circuit dia.)
• End stage amplifier to boost the signal
• Level detector outputs a pulse almost equal to
supply voltage when input crosses the limit
• Vcc held at 5V
(circuit dia.)
CEMI-2010, CSIO, Chandigarh
(results)
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Microcontroller section:
VIT University, April 2010
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Servo working:
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
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Design of the Hand:
Appearance:
• An endo-skeletal model for better functionality
• Two movable fingers and three “dummy” fingers
• Each finger having one DOF
• Gloves can be used to resemble skin
(DOF)
Mechanism:
• Spring loaded skeletal system
• Tendon driven mechanism
• DC servo motors used for enhanced controlling
• Each finger can be controlled by two motors
(design)
CEMI-2010, CSIO, Chandigarh
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Character segmentation:
(flow chart)
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The Letters ….>
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The whole setup
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Conclusion:
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
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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 KajangPuchong 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….
CEMI-2010, CSIO, Chandigarh
(title)
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EMG characteristics :
•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)
CEMI-2010, CSIO, Chandigarh
Bessel’s Filter chara:
(back)
CEMI-2010, CSIO, Chandigarh
EMG circuit diagram :
• Fourth order Bessel’s filter
Butterworth
Bessel
Chebyshev (0.5 dB)
Design of HPF
K(gain)
Fn
K(gain)
Fn
2
1.586
1.272
1.268
1.231
1.842
4
1.152
2.235
1.432
1.606
1.084
1.759
0.597
1.031
1.582
2.660
1.068
1.586
2.483
1.607
1.692
1.908
1.040
1.364
2.023
0.396
0.768
1.011
1.537
2.448
2.846
FC = fn / (2πRC)
Design of LPF
FC = 1 / (2π fn RC)
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CEMI-2010, CSIO, Chandigarh
(back)
K(gain)
Detector section:
•Voltage threshold of 1V was given
• Pulses equivalent to Vcc is
produced when input crosses the
limit
Design
V1 = (VCC x R2) / (R1 + R2)
CEMI-2010, CSIO, Chandigarh
(back)
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
(back)
CEMI-2010, CSIO, Chandigarh
As DOF increases, the complexity also
increases
Complexity increased by increase in
the number of actuators
Source: http://www.shadowrobot.com
Single DOF robotic hands are also
available
CEMI-2010, CSIO, Chandigarh
Robot hand
Structures
and
materials
BH8-series DIST Hand
Barrett
Universita
hand
di Genova
Barrett
Italy
technology,
inc. USA
3 fingers
(opposable),
Electrical
revolute
brushless
motors,
Spur and
worm gear
transmission
Fair contact
surface
smoothness
3 fingers
and one
opposable
thumb,
Electrical
revolute
brushless
motors,
Tendons
routed
through
pulleys
Robonaut
Hand
NASA
Johnson
Space
Center
USA
DLR Hand Ultralight
II
Hand
DLRResearch
German
center of
Aerospace Karlsruhe
Center
Germany
Germany
GIFU Hand
Gifu
University
Japan
Shadow
Hand
Shadow
Robot
Company
Ltd
UnitedKingdom
4 fingers
4 fingers
4 fingers
4 fingers
4 fingers
and one
and one
and one
and one
and one
opposable
opposable
opposable
opposable
opposable
thumb,
thumb,
thumb,
thumb,
thumb,
Electrical
Electrical
Flexible
Built-in DC Air
revolute
revolute
fluidic
Maxon
Muscles,
brushless
motors,
actuators,
servomotors Tendons,
motors,
Harmonic
Direct drive Worm gear Layer of
Flex-shaft + drives/gears transmission transmission soft
lead screw
transmission Silicones
polyurethan
transmission Silicone
rubber glove
e flesh, Thin
Kevlar body finger
polycarbona
armor
surface
te
coated with
fingernails
Teflon
UB Hand
III
Bologna
University
Italy
4 fingers
and one
opposable
thumb,
DC brushed
motor,
Pulling
tendons,
Continuous
compliant
pulps
Source: http://www.shadowrobot.com
CEMI-2010, CSIO, Chandigarh
(back)
Design of the Hand:
•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
CEMI-2010, CSIO, Chandigarh
• 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:
• 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:
…Noisy signals…
•EMG can always be affected by noise
• Proper insulation or noise reducing
cables should be used
CEMI-2010, CSIO, Chandigarh
Detector section:
•Voltage detector output is seen as
pulses
• These pulses will be driving
microcontroller
(back)
CEMI-2010, CSIO, Chandigarh