File - A Transradial Prosthetic Arm

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First found May 22, 2018

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Transradial
Prosthetic Arm
Kranti Peddada
Team Members: Kendall Gretsch and Henry Lather
Mentors: Dr. Charles Goldfarb and Dr. Lindley Wall
Website: www.transradialprostheticarm.weebly.com
Abbreviated Design
Specifications
• Patient Population
• Unilateral, transradial limb difference
• Ages 5+
• Total Parts Cost
• Maximum $150
• Functionality
• Hand and thumb open and close at mouth, belt, and in front
• Independent thumb movement with key grip
• Ability to lift and hold at least 500 g
• Weight
• Does not exceed weight of missing limb
New Design Specifications
• Do-it-yourself, open-source manufacturing and assembly
• Robohand Project distribution model
• Primarily through online support groups
• Advantages
•
•
•
•
•
Rapid distribution
Wide audience
Low cost
Highly customizable
Avoids hassles of regulations
• Kept in mind when choosing component of final design
Overview of Design
Inertial
Measurement
Unit (IMU)
Velcro
strap
Wire
Battery Pack
Overview of Design
Analytic Efforts
IMU and Sampling Rate
•
•
•
•
IMU from Prof. James Bobrow of UC Irvine
Internal update rate of 250 Hz using SPI transmission
No disadvantages in using maximum sampling rate
250 Hz chosen
2.54 cm
Power Requirements
•
•
•
•
IMU = 72 mA
Arduino Micro = 28 mA
Motors at rest = 6.4 mA (x5)
Motors at peak torque and angular velocity = 428 mA (x5)
• At rest ≈ 132 mA
• At peak ≈ 2.2 A
• Chosen voltage regulator can handle constant current of 3 A
(maximum of 5 A)
Torque Requirements
 = 0 =  − 0.98  3 sin 30° + 2 cos 15° + 2 cos 15°
 = 5.26  = 0.536 
Our motors can supply up to 2.2 kg-cm
Specific Details
IMU Operation
• Outputs yaw, pitch, roll, their time derivatives, and linear
acceleration in x, y, and z axes
Up/Down Shoulder Movement
Fwd./Rev. Shoulder Movement
Software Flow Chart
Device ON
Initialization:
Roll angle read
Read IMU Data
IF:
• Hand closed
• Thumb
closed
• Shoulder up
IF:
• Hand open
• Thumb
closed
• Shoulder
down
IF:
• Hand closed
• Thumb
closed
• Shoulder
forward
IF:
• Hand closed
• Thumb open
• Shoulder
backward
Hand OPEN
Hand CLOSED
Thumb OPEN
Thumb CLOSED
Hand
Socket
Total Assembly
Safety
• No major safety concerns anticipated
•
•
•
•
Only DC current used
All materials are non-toxic
NiMH batteries are safe
Motors kept distal from residual limb
Costs
Item
Inertial
measurement unit
Velcro straps
Stranded 18 AWG
wire
Printed circuit
board
Heat shrink tubing
Item
Quantity
(# or #
pkgs.)
Total Cost
Micro servo motor
Electrical tape
Fishing line
Elastic cord
(stringing)
1
1
$ 24.99
$ 4.15
1
$
9.24
1
1
$
$
2.43
2.28
AA battery holder
AA NiMH
rechargeable
batteries
1
$
7.51
8
$ 30.88
AA battery charger
5V switching
voltage regulator
2
$ 26.77
#216-1/2" screw eye
Adhesive wrap
1
$ 12.55
Total
ABS filament
Superglue
#6 lock washers
#6-32 cap nuts
#8 3/8" set screws
#8-32 1/2" machine
screws
#8-32 screw nuts
#6-32 6" threaded
rod
Quantity
(# or #
pkgs.) Total Cost
5
1
1
$ 46.49
$ 0.76
$ 2.51
1
$
1.63
n/a
1
12
2
6
$
$
$
$
$
6.20
2.49
1.29
2.59
2.33
12
8
$
$
2.59
2.59
1
$
3.06
4
1
$
$
1.29
3.75
$ 226.12
3D Printing and Assembly
• All parts are off-the-shelf or can be shipped in 2-5 business
days
• Socket and hand are 3D printed
• Less than 15 hours of printing time
• Basic soldering experience required
• Basic proficiency with hand-held electric tools required
• Fitting should be overseen by a Certified Prosthetist
The Prototype
Evaluation of Prototype
• Patient Population
• Unilateral, transradial limb difference
• Ages 5+
• Total Parts Cost
• $226.12
• Functionality
• Hand and thumb open and close at mouth, belt, and in front
• Independent thumb movement with key grip
• Ability to lift and hold 50 g (still testing)
• Weight
• Weighs 240 g
Intellectual Property
• Yes!
• New, useful, and non-obvious
• However, we want our design to be open-source
• Creative Commons License
• GNU General Public License
What We Learned
• Specific Skills
• Henry: Arduino boards, Arduino IDE, SPI transmission, PWM
motor control, power supplies, general embedded systems
• Kendall: prototyping mechanical systems, Autodesk Inventor,
using electric power tools
• Kranti: theory of servo and stepper motor control, microcontroller design and theory
• Keep design notebooks up-to-date
• Use Pugh charts to choose design
• 1 electrical engineer + 1 mechanical engineer + 1 computer
engineer > 3 biomedical engineers
Future Directions
•
•
•
•
•
•
Continue prototyping
Deliver finished prototype to Dr. Goldfarb and Dr. Wall
Find suitable candidate to further test device
Make adjustments as needed
Give candidate the device
Publish all designs and instructions to the internet
Acknowledgements
• Prof. Humberto Gonzalez
• Patricia Widder
• Our mentors:
• Dr. Charles Goldfarb
• Dr. Lindley Wall
Thank You
• Questions?
×

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