Department of Electrical Engineering, Institute of Technology
“Sepuluh Nopember” (ITS), Surabaya, Indonesia
840-8502, Japan
e-mail: arai@is.saga-u.ac.jp
on Arti? cial Life and Robotics, Oita, Japan, February 5–7, 2009
However, it is sometimes dif? cult for a person with a physi-
cal disability. Nowadays, an electric wheelchair is commer-
cially available for disabled people. It generally requires
considerable skill to operate. Moreover, some disabled
people cannot drive an electric wheelchair manually, even
with a joystick, because they lack the physical ability to
control the movement. To enable a disabled person to drive
a wheelchair safely and easily so that they can enjoy a
higher quality of life, researchers have proposed several
electric wheelchair systems. The use of voice commands to
control an electric wheelchair is one research result. A small
number of command words and high-performance voice
recognition are employed in this system. An electric wheel-
chair control with electro-oculography (EOG) techniques
has also been proposed. In this case, the different com-
mands for the wheelchair are derived from the electro-ocu-
lography (EOG) potential signals of eye movements.
A camera is set up in front of the wheelchair user to capture
gaze direction and eye blinking. A camera is set up in front
of a wheelchair user to capture image information. The
sequential captured image is interpreted to obtain the gaze
direction and eye blinking properties. The gaze direction is
expressed by the horizontal angle of the gaze, and this is
derived from the triangle formed by the centers of the eyes
and the nose. The gaze direction and eye blinking are used
to provide direction and timing commands, respectively.
The direction command relates to the direction of move-
ment of the electric wheelchair, and the timing command
relates to the time when the wheelchair should move. The
timing command with an eye blinking mechanism is designed
to generate ready, backward movement, and stop com-
mands for the electric wheelchair. Furthermore, to move at
a certain velocity, the electric wheelchair also receives a
velocity command as well as the direction and timing com-
mands. The disturbance observer-based control system is
used to control the direction and velocity. For safety pur-
poses, an emergency stop is generated when the electric
wheelchair user does not focus their gaze consistently in any
direction for a speci? ed time. A number of simulations and
experiments were conducted with the electric wheelchair in
a laboratory environment.
Blinking measurement
the face area of the wheelchair user. The camera is con-
nected to a computer with vision processing and electric
wheelchair motion control capabilities. With vision process-
ing, the sequential captured image is interpreted to obtain
the gaze direction and eye blinking properties. The gaze
direction is expressed as the horizontal angle of the user’s
gaze, and is derived from the triangle formed by the centers
of the eyes and the nose. The eye-blinking properties are
obtained from the timing of blinks. The gaze direction and
eye blinking are used to provide the direction and timing
commands, respectively, for the electric wheelchair. The
direction command relates to the direction of movement of
the electric wheelchair, and the timing command relates to
the time when the electric wheelchair should move. The
eye-blinking mechanism with a blink duration of at least
400 ms is designed to generate a timing command for when
to move. Furthermore, the electric wheelchair also receives
a velocity command to move at a certain velocity, as well
as the direction and timing commands. The disturbance
observer-based control system is used to control the direc-
tion and velocity. For safety purposes, an emergency stop
is generated when the electric wheelchair user does not
focus their gaze consistently in one direction for a speci? ed
time.
the wheelchair. The electric wheelchair uses a differential
steering mechanism. The wheelchair design considers the
following four important factors: safety, ease of operation,
low price, and convenience.
signal applied to the motor of each wheel. The angular
velocities
the right, respectively. The relation between direction and
velocity (
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eyes and the nose
measurement noise.
timing command which can be applied directly to the con-
troller. Eye blinking with a duration of at least 400 ms is
used as the timing command. The algorithm of the timing
command is as follows:
2. If <2 blinks>then <enable controller>
3. If <long blinking>then <set to move backward>
electric wheelchair user and the performance of the vision
system. “Bad” behavior is de? ned as when the user does
not focus during wheelchair control. Failure of the vision
system occurs when the system fails to detect the user’s face.
The safety command algorithm is de? ned as
controller>
technique is applied. The disturbance observer is a tech-
nique to estimate the disturbance existing in a plant, and to
make the motion controller be an acceleration controller
also.
of the controller is realized by constant gain K.
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tion reference generator
lated in Eq. 1. Furthermore, the acceleration reference can
be derived from Eq. 1 as follows:
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the eyes and the nose can be formulated to generate a direc-
tion command for the electric wheelchair. Combining the
direction, velocity, timing, and safety commands yields an
effective method of controlling an electric wheelchair. With
the disturbance observer technique applied as a control
strategy, the design criteria of the wheelchair control system
can easily be satis? ed.
niques and Applications, December 2007, Kobe, Japan
acquired with relatively cheap web camera allowing user move-
ments. J Inst Elec Eng Jpn C-127(7):1107–1114
56–67