A Semi-Powered Ankle Prosthesis and Unified Controller for Level and Sloped Walking

Area of Science:

• Biomechanics
• Robotics
• Prosthetics

Background:

• Healthy walking exhibits invariant external quasi-stiffness across different terrains.
• Existing prostheses often struggle to adapt to varying ground slopes without parameter adjustments.
• Ankle stiffness control is crucial for replicating natural gait dynamics.

Purpose of the Study:

• To develop and evaluate a semi-powered ankle prosthesis with a unified controller for biomimetic walking on level and sloped surfaces.
• To emulate invariant external quasi-stiffness observed in healthy individuals during walking.
• To assess the prosthesis's performance without requiring ground slope identification or control parameter modulation.

Main Methods:

• Development of a semi-powered ankle prosthesis featuring a novel constant-volume power-asymmetric actuator.
• Implementation of a unified controller designed to vary ankle stiffness set-point.
• Testing the device and controller on three transtibial amputees across inclines, level ground, and declines.

Main Results:

• The semi-powered ankle prosthesis and unified controller demonstrated consistent external quasi-stiffness.
• Performance was comparable to healthy subjects across all tested ground slopes (inclines, level, declines).
• The system successfully provided biomimetic behavior without explicit slope detection.

Conclusions:

• The developed semi-powered ankle prosthesis and unified controller effectively replicate healthy ankle quasi-stiffness during level and sloped walking.
• This approach offers a promising advancement in prosthetic technology for improved gait adaptability and naturalness.
• The findings support the controller's ability to provide consistent gait dynamics irrespective of terrain variations.