Robot-Assisted Adaptive Training: Custom Force Fields for
Teaching Movement PatternsPatton and Mussa-Ivaldi
(2004) Robot-Assisted
Adaptive Training: Custom Force Fields for Teaching Movement Patterns, IEEE Transactions on Biomedical Engineering
51(4): 636-646 TBME-00072-2002.R2
Abstract— Based on recent studies of neuro-adaptive control, we tested a new
iterative algorithm to generate custom training forces to “trick” subjects into
altering their target-directed reaching movements to a pre-chosen movement as
an after-effect of adaptation. The pre-chosen movement goal, a
sinusoidal-shaped path from start to end point, was never explicitly conveyed
to the subject. We hypothesized that the adaptation would cause an alteration
in the feedforward command that would result in the pre-chosen movement. Our
results showed that when forces were suddenly removed after a training period
of 330 movements, trajectories were significantly shifted towards the
pre-chosen movement. However, de-adaptation occurred (i.e., the after-effect
"washed out") in the 50-75 movements that followed the removal of the
training forces. A second experiment suppressed vision of hand location and
found a detectable reduction in the washout of after-effects, suggesting that
visual feedback of error critically influences learning. A final experiment
demonstrated that after-effects were also present in the neighborhood of
training -- 44% of original directional shift was seen in adjacent, unpracticed
movement directions to targets that were 60 different from
the targets used for training. These results demonstrate the potential for
these methods for teaching motor skills and for neuro-rehabilitation of
brain-injured patients. This is a form of “implicit learning,” because unlike
explicit training methods, subjects learn movements with minimal instructions,
no knowledge of, and little attention to the trajectory.
Index Terms— Human, Motor learning, Adaptation, Control, Force fields, Robots,
Haptics, Human-machine interface, Teaching, Robotic neurorehabilitation.
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