@article{GawLakLor08,
author = {P.J. Gawthrop and M.D. Lakie and I.D. Loram},
title = {Predictive Feedback Control and {Fitts'} Law},
journal = {Biological Cybernetics},
year = 2008,
volume = 98,
number = 3,
pages = {229-238},
month = {March},
note = {Published online: 5 January 2008},
doi = {10.1007/s00422-007-0206-9},
abstract = {
Fitts' law is a well established empirical formula, known for
encapsulating the ``speed-accuracy trade-off''. For discrete, manual
movements from a starting location to a target, Fitts' law relates
movement duration to the distance moved and target size. The
widespread empirical success of the formula is suggestive of
underlying principles of human movement control. There have been
previous attempts to relate Fitts' law to engineering-type control
hypotheses and it has been shown that the law is exactly consistent
with the closed-loop step-response of a time-delayed, first-order
system. Assuming only the operation of closed-loop feedback, either
continuous or intermittent, this paper asks whether such feedback
should be predictive or not predictive to be consistent with Fitts
law. Since Fitts' law is equivalent to a time delay separated from a
first-order system, known control theory implies that the controller
must be predictive. A predictive controller moves the time-delay
outside the feedback loop such that the closed- loop response can be
separated into a time delay and rational function whereas a non-
predictive controller retains a state delay within feedback loop
which is not consistent with Fitts' law. Using sufficient
parameters, a high-order non-predictive controller could
approximately reproduce Fitts' law. However, such high-order,
``non-parametric'' controllers are essentially empirical in nature,
without physical meaning, and therefore are conceptually inferior to
the predictive controller. It is a new insight that using
closed-loop feedback, prediction is required to physically explain
Fitts' law. The implication is that prediction is an inherent part of
the ``speed-accuracy trade-off''.
}
}
@article{GawNeiGonWag08,
author = {P.J. Gawthrop and S.A. Neild and A. Gonzalez-Buelga and D.J. Wagg},
title = {Causality in real-time dynamic substructure testing},
journal = {Mechatronics},
year = 2010,
volume = 19,
number = 7,
pages = {1105--1115},
month = {October},
note = {Available online 16 April 2008},
abstract = { Causality, in the bond graph sense, is shown to provide
a conceptual framework for the design of real-time
dynamic substructure testing experiments. In
particular, known stability problems with
split-inertia substructured systems are
reinterpreted as causality issues within the new
conceptual framework. As an example, causality
analysis is used to provide a practical solution to
a split-inertia substructuring problem and the
solution is experimentally verified.},
doi = {10.1016/j.mechatronics.2008.02.005}
}
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