Transcript The Advanced Prosthetic Hand Project

The Advanced
Prosthetic Hand
Project
Jessica Reddy, IMSURE Fellow
Mentor: Dr. William C. Tang
Jessica’s Journey…
•
Hurdles:
1. Bio-major’ness
•
I know how a muscle works, but an artificial muscle?
2. Purchasing FEMLAB
3. Where do I begin?
•
Solutions:
1. Read, read, and read.
2. Solved.
3. Grad Student! (Shawn)
Current Artificial Limb
Technology
• Myoelectric Prostheses
– Electrode in prosthesis
socket detects EMG
signals from residual
muscle remnant
– Prosthetic Hook
• Thumb-index finger pinch
Sgt. Joseph Bozik
Walter Reed Medical Center
Proposed Advancements
• Implantation of Neural Prosthetic into:
– Brachial Plexus nerve (short term goal)
– Cortical brain area (long term goal)
• Multiple sites
• Develop a prosthetic hand with multiple
degrees of freedom
– Use skeletal model of human hand for frame
– Tactile sensing
– Low weight, low energy consumption
Pneumatic Artificial Muscle
• Contractile and linear motion engine operated by gas
pressure
• Flexible closed membrane attached at both ends to
fittings
• Mechanical power is transferred to a load
Pneumatic Artificial Muscle
Course of action:
•As contraction , volume to max force to 0 &
contraction max
Characterization of the Optimal
Artificial Muscle
Generated force depends on…
• Type of membrane
– Geometry
– The way it inflates
• Length
• Gauge pressure
Braided Muscles
• Gas-tight elastic tube surrounded by a braided
shell
• Braid fibers run helically about the muscle’s
longitudinal axis at an angle
• When pressurized the tube presses laterally
against the shell
Mckibben Artificial Muscle
• Muscle contracts axially
– (With lateral expansion)
• Causes pulling force on its load
Mckibben Artificial Muscle
Drawbacks:
1. Friction between braid and tube
•
2.
3.
4.
5.
6.
Hysteresis
Requires complex control algorithm
Deformation of rubber tube
Pressure Threshold
Flaws in membrane material
Maximum displacement is limited.
•
20-30% contraction
7. Low force output
•
650 N (rest); 300 N (15% contraction); 0 N (30%
contraction)
–
Applied pressure: 300 kPa, length=15 cm; rest diameter=1.4cm
Building a more suitable
design…
1. Avoid friction: use a single layer actuator
2. Therefore, simplifying the control
3. Avoid deformation: use membrane material
with high tensile stiffness
4. No pressure threshold: use elastic membrane
material
Building a more suitable
design…
• Want little stress in lateral direction to
minimize elastic deformation (strain)
• How to achieve lateral expansion with a
high tensile stiffness material?
• Rotationally repeated pattern
 Pleats
Pleated Pneumatic Artificial
Muscle
• Pack membrane into many folds along axis of
muscle
• Maximum displacement: 40-50%
• Force output:
– 3,300 N at 5% contraction; 1,300
N at 20% contraction; 0 N at 43%
contraction
 Applied pressure: 300 kPa,
length=10 cm, diameter=2.5 cm
With these considerations in
mind, let’s build a model!
Kevlar 49:
• High tensile strength
• High elastic modulus
• Low density
Y-Displacement Throughout Cross
section
X-Displacement Throughout Cross
section
Upcoming endeavors…
• Introduce pleats
• Represent other layers of muscle
– Polyproylene lining
• Extend model to 3D
– Include End Fittings
• Miniaturization of the Artificial Muscle
UCI Subsystem Development Team
Members
Pending DARPA Award.
Artificial Muscle
• William C. Tang (Team Lead), Professor, Biomedical Engineering
Department, Electrical Engineering & Computer Science Department
– Ryan Langan, UROP SURP Fellowship
Neural Interface
• William E. Bunney, Distinguished Professor & Co-Chair, Department of
Psychiatry & Human Behavior
• James H. Fallon, Professor, Department of Anatomy and Neurobiology
Communications
• Payam Heydari, Assistant Professor, Department of Electrical Engineering
& Computer Science
Tactile Sensor
• Abraham P. Lee, Professor, Biomedical Engineering Department,
Mechanical & Aerospace Engineering Department
Interface and Algorithm
• Zoran Nenadić, Assistant Professor, Biomedical Engineering Department
Please visit our website:
www.advancedprosthetichand.com
Dr. William C. Tang
Webmaster: Ryan Langan