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LOWER-LIMB WEARABLE ROBOTICS

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
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  • 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

 

Forward and Backward Walking on the UT Dallas Powered Prosthetic Leg
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Forward and Backward Walking on the UT Dallas Powered Prosthetic Leg

The robotic prosthetic leg is synchronized to the user's thigh motion, allowing forward and backward walking at varying speeds.
Amputee Fast Walking up to 3.0 mph on the UTD Powered Prosthetic Leg
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Amputee Fast Walking up to 3.0 mph on the UTD Powered Prosthetic Leg

The powered knee-ankle prosthesis is synchronized to the user's hip motion, allowing seamless adjustments in walking speeds up to 3.0 mph. This work was conducted by the Locomotor Control Systems Laboratory under the direction of Prof. Robert Gregg with financial support from the National Institutes of Health, the National Science Foundation, and the Burroughs Wellcome Fund.
Amputee Subject Walking Backwards on UTD Powered Prosthetic Leg
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Amputee Subject Walking Backwards on UTD Powered Prosthetic Leg

The powered knee-ankle prosthesis is synchronized to the user's hip motion, allowing seamless transitions between forward and backward walking. This work was conducted by the Locomotor Control Systems Laboratory under the direction of Prof. Robert Gregg with financial support from the National Institutes of Health, the National Science Foundation, and the Burroughs Wellcome Fund.
Non-Rhythmic Activities with a Powered Prosthetic Leg
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Non-Rhythmic Activities with a Powered Prosthetic Leg

These experiments demonstrate volitional activities with a robotic prosthetic leg that is controlled by a user-synchronized phase variable. Research supported by the National Institutes of Health and the Burroughs Wellcome Fund.
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