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 FEMLAB3. 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

Course of action:

•As contraction , volume to max force to 0 & contraction max

Pneumatic Artificial Muscle

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

Drawbacks:1. Friction between braid and tube

• Hysteresis

2. Requires complex control algorithm3. Deformation of rubber tube4. Pressure Threshold5. Flaws in membrane material6. 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

Mckibben Artificial Muscle

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…

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

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

Pending DARPA Award.Pending DARPA Award.

Please visit our website:www.advancedprosthetichand.com

Webmaster: Ryan LanganDr. William C. Tang