Design and Characterization of a Quasi-Passive Pneumatic Foot-Ankle Prosthesis

Area of Science:

• Biomedical Engineering
• Prosthetics and Orthotics
• Robotics

Background:

• Current passive prosthetic feet lack the biomimetic joint mechanics of the intact human ankle.
• The cantilever design of many prosthetics results in stiffness characteristics that differ from the biological ankle's stance phase.
• There is a need for prosthetic devices that can replicate the dynamic behavior of the human ankle during locomotion.

Purpose of the Study:

• To introduce the design and control of a novel pneumatic foot-ankle prosthesis.
• To achieve biomimetic joint mechanics that better replicate the intact human ankle.
• To customize prosthetic ankle mechanics through adjustable pneumatic pressure.

Main Methods:

• Design of a pneumatic prosthesis featuring a cylinder in series with a fiberglass leaf spring and a solenoid valve.
• Utilizing a solenoid valve as a mechanical clutch for resetting the ankle's equilibrium position.
• Employing a mechanical testing machine to compare torque-angle curves with a passive prosthetic foot and testing with a transtibial amputee.

Main Results:

• The pneumatic prosthesis demonstrated an appropriate range of motion during walking trials.
• The device achieved a maximum torque output of 94 Nm.
• The prosthesis returned approximately 11.5 J of energy during testing.

Conclusions:

• The developed pneumatic foot-ankle prosthesis offers a promising approach to achieving biomimetic ankle mechanics.
• Adjustable pneumatic pressure allows for customization of prosthetic ankle behavior.
• The prosthesis shows potential for improving gait in individuals with transtibial amputations.