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This project is
focused on the development and testing of a new type of portable
and controllable Active Knee Rehabilitation Orthotic Device (AKROD)
for gait retraining in stroke patients. Two different components
of the device have been developed: a resistive (variable damper)
and an active (torque actuator) component. The variable damper
component of the brace is used to facilitate knee flexion during
stance by providing resistance to knee buckling. Furthermore,
the knee brace is used to assist in knee
control during swing, i.e. to allow patients to achieve adequate
knee flexion for toe clearance and adequate knee
extension in preparation to heel strike. The torque actuator
component is used to encourage patients to actively extend the knee during
mid-to-terminal stance, facilitate knee flexion during initial
swing, and again encourage knee extension during mid-to-terminal
swing.
The knee brace is composed of straps and rigid components for
attachment to a leg, with a central hinge mechanism where a gear
system is connected.
The key
features of the AKROD include: a compact, lightweight design
with strong, highly tunable torque capabilities, full
portability with on board power, control circuitry, sensors, and
real-time closed loop computer control for optimizing
rehabilitation exercises while in use. The variable damper
component is achieved through an electro-rheological fluid (ERF)
element that connects to the output of the gear system.
Concentric cylinders, acting as electrodes supply the necessary
electric field to activate the fluid, which changes its
consistency from that of a fluid to a thick
viscoelastic gel.
Simultaneously, these plates, when charged and rotating, act as
surfaces upon which the activated fluid creates a shear force in
response to rotation. An advanced actuator that uses the
Gear Bearing Drive concept (see section on Advanced Actuators)
was developed to generate torque.
Algorithms for establishing appropriate control of the knee
brace are also being developed. Using data from both normal
volunteers and hemiplegic stroke survivors, we are creating
training programs for the knee orthosis to assist patients in
re-establishing a natural gait pattern. |
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