Hybrid Invariance and Stability of a Feedback Linearizing Controller for Powered Prostheses

Area of Science:

• Biomedical Engineering
• Robotics
• Control Systems

Background:

• Powered lower-limb prostheses offer significant quality of life improvements for amputees.
• Existing control schemes have primarily focused on specific gait phases, like the stance period.

Purpose of the Study:

• To investigate the application of hybrid zero dynamics (HZD) for controlling the entire gait cycle in lower-limb prostheses.
• To demonstrate feedback linearization using only on-board sensor data.
• To develop a metric for assessing the orbital stability of periodic gaits.

Main Methods:

• Utilized hybrid zero dynamics (HZD) control principles, originally developed for bipedal robots.
• Implemented feedback linearization using sensor data exclusively from on-board sensors.
• Developed an analytical metric to evaluate the orbital stability of two-step periodic gaits.
• Simulated the controller's performance across the complete gait cycle.

Main Results:

• An HZD-based controller successfully managed the entire gait cycle in simulations.
• Feedback linearization was achieved using only on-board sensor information.
• An analytic metric for orbital stability of periodic gaits was successfully developed.

Conclusions:

• HZD-based control is viable for comprehensive gait cycle management in powered lower-limb prostheses.
• On-board sensors are sufficient for implementing feedback linearization in these prostheses.
• The developed stability metric provides a valuable tool for analyzing prosthetic gait.