Design, Characterization, and Preliminary Assessment of a Two-Degree-of-Freedom Powered Ankle-Foot Prosthesis

Area of Science:

• Biomedical Engineering
• Rehabilitation Robotics
• Biomechanics

Background:

• Powered ankle prostheses enhance walking economy in transtibial amputees.
• Current commercial prostheses offer limited one-degree-of-freedom motion.
• Frontal plane motion (eversion/inversion) is crucial for balance during ambulation.

Purpose of the Study:

• To design, build, and evaluate an untethered, two-degree-of-freedom (2-DoF) powered ankle-foot prosthesis.
• To enable active control of plantarflexion, dorsiflexion, eversion, and inversion.
• To provide a platform for studying ankle-subtalar-foot complex biomechanics and function recovery.

Main Methods:

• Developed a 2-DoF powered ankle-foot prosthesis with active control for multiple motions.
• Conducted benchtop tests to characterize system dynamics and actuator performance.
• Performed level-ground walking trials with a unilateral transtibial amputee to assess real-world performance.

Main Results:

• Benchtop tests showed a step response rise time under 50 ms and a closed-loop torque bandwidth of 9.74 Hz.
• Walking trials demonstrated torque tracking errors (RMS) below 7 N·m.
• The prosthesis exhibited adequate torque control and supported level-ground walking.

Conclusions:

• The developed 2-DoF powered ankle prosthesis effectively supports level-ground walking.
• The device offers potential for enhanced balance control and greater recovery of biological ankle function.
• This platform can advance research in amputee biomechanics and neural interface applications.