Biomedical Engineering Reference
In-Depth Information
fiber; 3) a controller (a personal computer system) which can calculate the
frequency of the electrical stimulation (a series of electrical pulse sequences)
that should evoke in the subject the same magnitude of pressure sensation
as is given to the pressure-conductive rubber of the robot hand, and which
can control the electrical stimulator so that it generates an electrical pulse
sequence with that frequency; and 4) a tungsten microelectrode which, when
inserted into the subject's nerve, can stimulate a single nerve fiber coming
from a mechanoreceptor unit. The schematic diagram is shown in Fig. 4.61.
When pressure was applied to the pressure-conductive rubber, the per-
sonal computer (controller) modulated the output voltage of the pressure-
conductive rubber to the frequency of the electrical pulses for stimulating
the sensory nerve fiber; it controlled the electrical stimulator so that it could
output the above-mentioned electrical pulses. The sensory nerve fiber was
stimulated by the electrical pulses via the tungsten microelectrode, and the
same afferent signal (as should be evoked when the pressure was applied to
the mechanoreceptor unit itself) was evoked in the nerve fiber, making the
subject evoke a pressure sensation at the projected area.
Just before the experiment to convey sensation via the artificial arm sy-
stem, we evaluated the quantitative relationship between the frequency of
the electrical stimulation and the intensity of the evoked pressure sensation
using the magnitude estimation method with the same subject; in addition,
we determined the equation to calculate frequency of the electrical stimula-
tion from the output voltage of the conductive rubber.
The subjective intensities of the sensations evoked by the electrical sti-
mulation were described by the subjects using a slide volume (Fig. 4.62),
and these subjective evaluations were then compared with the strengths of
the stimuli that were applied to the pressure-conductive rubber of the robot
hand.
The system worked satisfactorily. The subjects were able to feel pressure
sensations resulting from the pressure applied to the conductive rubber of the
Fig. 4.60.
The prototype of the artificial arm system developed in our study; the
palm and fingers of the arm system were covered with pressure-conductive rubber
in order to detect pressure applied to the arm system
