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Research Overview

Amputees generally have an asymmetric gait, higher metabolic consumption, and are prone to falling with a passive prosthesis. Our research is driven by designing a powered knee-ankle prosthesis and developing human-inspired control strategies for above-knee amputees to walk in a stable, able-bodied manner. The proposed work is designing a time-invariant, phase-based controller, which require no retuning of control parameters independent of the patient or task. Here are the aims of this research work.

  1. Develop a unified controller that systematically captures both stance and swing period of human walking for a powered prosthesis.

  2. Design and build a powered knee-ankle prosthesis validating implementation of the unified control strategy for real-time control.

  3. Perform human experiments to demonstrate the clinical feasibility of the unified controller with multiple amputee subjects using a powered prosthesis.


A Unified Virtual Constraint Control for a Powered Knee-Ankle Prosthesis
  • To provide control to a multi-joint powered prosthesis, we developed a new class of virtual constraints unified over the gait cycle while respecting the continuous, periodic nature of human walking.

  • Feedback linearization was implemented for the prosthesis controller and validated using an amputee biped model. Each walking speed produced asymptotically stable gaits.

Design and Manufacturing of a Powered Knee-Ankle Prosthesis
  • The powered prosthesis contains high-torque actuators for both knee and ankle joints with on-board sensors.

  • The prosthesis design met the joint kinematics and kinetics requirements for amputees to ambulate as an able-bodied.

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Amputee Experiments of using the Phase-Based Unified Controller


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