A Phase Variable Approach to Volitional Control of Powered Knee-Ankle Prostheses.

Area of Science:

• Biomedical Engineering
• Robotics
• Prosthetics and Orthotics

Background:

• Current multi-joint prosthetic leg control excels at periodic tasks like walking.
• Controlling prosthetic legs for non-periodic, volitional movements remains a significant challenge.
• Existing systems often lack the adaptability for diverse, real-world maneuvers.

Purpose of the Study:

• To develop a novel controller for multi-joint prosthetic legs capable of both periodic and non-periodic tasks.
• To enable seamless transitions between different leg motions for enhanced user control.
• To improve the functionality and adaptability of powered prostheses for transfemoral amputees.

Main Methods:

• A finite state machine (FSM) was employed, utilizing a piecewise holonomic phase variable.
• The phase variable was derived from thigh angle measurements.
• FSM transitions were triggered by foot contact sensing and reference gait trajectory attributes.

Main Results:

• The controller was successfully implemented on a powered knee-ankle prosthesis.
• A transfemoral amputee subject demonstrated proficiency in various tasks: walking (low/high speed), starting/stopping, backward walking, obstacle negotiation, and ball kicking.
• The system exhibited robust performance across a spectrum of periodic and non-periodic leg movements.

Conclusions:

• The proposed controller effectively integrates periodic and non-periodic leg motions for prosthetic applications.
• This approach offers a pathway to more intuitive and reliable volitional control of multi-joint prostheses.
• The findings are expected to advance the development of prosthetics capable of a wider range of human-like movements.