Virtual finger
The concept of the virtual finger has been postulated as an abstract
representation through which the human brain plans grasping tasks [1].
The virtual finger is a functional unit comprised of at least one real
physical finger (which may include the palm); the real fingers comprising a
virtual finger act in unison to apply an opposing force on the object and
against the other virtual fingers in a grasp. This effectively reduces the
many degrees of the human hand to those that are deemed necessary to perform
the grasping task. This concept replaces the analysis of the mechanical
degrees of freedom of individual fingers by the analysis of the functional
roles of forces being applied in a grasp.
In the example shown below, two fingers act against the same object surface;
they act in a similar manner, and can thus be regarded as a single virtual
finger.
The process of mapping the real fingers to virtual fingers is an important
one which enables both the
recognition
of volar (i.e., palmar) grasps
and the mapping from the human hand grasp to that of the manipulator.
Associated with the virtual finger is the concept of
opposition space.
Reference
- M.A. Arbib, T. Iberall, and D.M. Lyons, "Coordinated
control programs for movements of the hand,"
Hand Function and the Neocortex, eds. Goodwin, A.W., and
Darian-Smith, I., Springer-Verlag, 1985, pp. 111-129.