Article

We used a three-dimensional biomechanical model of human standing to test the
feasibility of feed-forward control systems that vary stimulation to paralyzed
muscles based on the user's posture and desire to effect a postural change. The
controllers examined were
(1) constant baseline stimulation, which represented
muscle activation required to maintain erect standing,
and (2) posture follower,
which varied muscle activation as a function of the location of the projection of
whole-body center of mass on the base of support. Posture-dependent control of
stimulation demonstrated significant benefits over open-loop stimulation. Posture
follower reduced upper-limb (UL) effort by an average of 50% compared with UL
effort alone and by an average of 34% compared with baseline stimulation. On the
other hand, reduction in UL effort was an average of 32% when using baseline
stimulation. Compared with using UL effort alone, both controllers result in more
than a 50% reduction in effort. The results of this study indicate that control
systems that facilitate user-driven, task-dependent postures can be more
effective and efficient than conventional open-loop stimulation. Also, they
obviate the need for complicated posture-setting devices such as switches and
joysticks. Functional implications include the potential to expand reachable
workspace and better preparation for anticipated disturbances that could
challenge balance over existing neuroprostheses for standing.

Langue : ANGLAIS