Variable Impedance Control of Powered Knee Prostheses Using Human-Inspired Algebraic Curves.

Area of Science:

• Biomedical Engineering
• Robotics
• Biomechanics

Background:

• Coordinated motion between transfemoral amputee patients and powered prosthetic joints is crucial for effective prosthesis control.
• Existing control strategies often lack adaptability to individual user gait dynamics.

Purpose of the Study:

• To develop a novel control strategy for powered knee prostheses using an algebraic curve representation of human walking data.
• To achieve seamless, coordinated hip-knee motion that adapts to user-specific gait variations.

Main Methods:

• An algebraic curve representing nominal human walking data was employed for controller design.
• A variable impedance scheme, designed using a parameter-dependent Lyapunov function, established a continuum of equilibria.
• A radial projection algorithm was developed to manage variability in user hip motion.

Main Results:

• The proposed control law successfully achieved coordinated hip-knee motion by continuously adapting spring and damper behaviors along the algebraic curve.
• The radial projection algorithm efficiently accommodated variations in user hip motion, enhancing adaptability.
• The controller demonstrated a velocity-independent holonomic relationship between human and prosthetic joints.

Conclusions:

• The algebraic curve representation provides a robust framework for powered knee prosthesis control.
• The variable impedance strategy and radial projection algorithm offer a promising approach for natural and adaptive prosthetic gait.
• This method enhances functional mobility for transfemoral amputees by enabling intuitive, coordinated joint movement.