Control Framework for Sloped Walking With a Powered Transfemoral Prosthesis.

Area of Science:

• Biomedical Engineering
• Robotics
• Biomechanics

Background:

• User customization of lower-limb prosthesis controllers is challenging.
• Current impedance control strategies require extensive tuning for different conditions.
• A direct relationship between joint control parameters and terrain slope is not well-established.

Purpose of the Study:

• To develop a novel control framework for powered transfemoral prostheses.
• To establish a predictable relationship between joint impedance parameters and walking slope.
• To enable intuitive and adaptive control for amputee gait.

Main Methods:

• A hybrid control framework combining impedance control and trajectory tracking was developed.
• Impedance functions (stiffness, damping) were modeled as polynomials derived from healthy human walking data.
• Principal Component Analysis (PCA) simplified these functions, revealing monotonic trends with slope angle.

Main Results:

• A clear relationship was identified between joint parameter functions and slope angle.
• The derived trends allow for controller design adaptable to any given slope.
• Powered transfemoral prosthesis trials demonstrated a healthy human gait in amputee users.

Conclusions:

• The proposed framework simplifies prosthesis control and customization.
• The established relationship between parameters and slope enables slope-adaptive control.
• The controller successfully replicated healthy human gait kinematics and kinetics across different slopes.