Bio-inspired design and validation of the Efficient Lockable Spring Ankle (ELSA) prosthesis

Area of Science:

• Biomedical Engineering
• Robotics
• Biomechanics

Background:

• Active lower-limb prostheses can restore physiological gait for transfemoral amputees.
• Current devices suffer from limited battery life, high weight, and cost, hindering user adoption.
• There is a need for active, affordable, lightweight, and energy-efficient prosthetic solutions.

Purpose of the Study:

• To develop an active prosthetic ankle that is lightweight, affordable, and energy-efficient.
• To restore natural ankle dynamics and improve gait for transfemoral amputees.
• To introduce the Efficient Lockable Spring Ankle (ELSA) prosthesis.

Main Methods:

• Development of a bio-inspired, stiffness-adjustable parallel spring with a servo-actuated ratchet and pawl mechanism.
• Integration of a rope-driven series elastic actuator for active push-off.
• Design focused on lightweight construction (1.2kg) and low cost.

Main Results:

• The ELSA prosthesis generates a physiological ankle torque pattern during level ground walking.
• Up to 50% of peak torque is achieved passively with minimal energy cost (0.1 J/stride).
• The system is designed to be lightweight and affordable.

Conclusions:

• The ELSA prosthesis offers a promising solution for transfemoral amputees by providing an active, energy-efficient, and cost-effective gait restoration device.
• The combination of passive and active components allows for significant torque generation with reduced energy consumption.
• This development addresses key limitations of current active prostheses, potentially increasing user acceptance and quality of life.