  Bilateral control, a remote-control technique, is used to work at a distance.
However, many existing bilateral control systems have two common problems: 1)
it is difficult to create a system like a human hand, that has multiple degrees
of freedom and 2) if the mechanism becomes too complicated, operators feel
restrained and experience discomfort. Because, for these reasons, the bilateral
control of fingers has not been accomplished to date, we aimed to overcome this
by applying functional electrical stimulation~(FES). In our experiments,
through an adhesive electrode pad, electrical stimulation was delivered to the
muscles that flex and expand the metacarpophalangeal joints of the thumb and
middle finger. Position-symmetrical bilateral control was implemented so that
the deviation of the master's and slave's positions relative to each other was
zero degrees. A sliding mode controller was used as a position controller. We
found it possible to control multiple degrees of freedom; however, we found
areas where the number of tracking errors was large. We speculated that the
middle finger did not bend, because the arm rotates as the thumb was abduction,
therefore the position of the motor point of the middle finger deviates from
the position of the pad.
