IEEE Circuits and Systems Magazine - Q3 2021 - 82

multiple experimental schemes. In the final version, an
innovative control logic is proposed to solve the problem
based on the monocular positioning algorithm. As
shown in Fig. 5, the wheelchair advances when the
user has only one eye open, and brakes automatically
when both eyes are open or closed. To reduce chances
of view obstruction, in the lower-left corner of the
wheelchair, a physical screen detects the position of
the focal length of user's eyes and assists the user to
give the turning instructions: when a certain turning
button has been gazed for more than 1s, the wheelchair
will automatically turn in the corresponding direction.
For control signals, 11 signals fed into the engine are
used to control the wheelchair motor, six of which are
responsible for the starting and the speed, while the
other five reflect direction adjustment. Three basic signals,
VCC, GND and Verf
(standard voltage), and two control
signals, SA
whenVV .
S 2 erf
AB,
B. SDK Secondary Development
In this subsection, we focus on the SDK secondary development,
which contains two main parts:
■ Unity SDK: To track the GPI, connect to the User
Interface (UI) and communication module, and
determine whether turning around.
■ Monocular SDK: To identify monocular movements
and determine whether to move forward.
According to the static class in Tobii.Gaming
Wi-Fi CPE
namespace, the TobiiAPI provides direct access to the
functionality of the Tobii Unity SDK framework2. For
further analysis of gaze focus detection, GazePoint and
HeadPose from the sensors are obtained, which represent
the user's gazing point on the screen, i.e., where the
user's eye-gaze intersects with the screen plane, and the
head position & rotation of the user's head, respectively.
After accurate calibration and head modeling, the collected
data are transmitted to the pre-loaded SDK program
(guided by Subsection IV-A), which realizes intent analysis
and robust control.
Dual Eye Trackers
Gaze Point
Microcomputers
Pose and Location
Gyroscope
Control Signal
Electrical Motors
Data Stream
V. Auxiliary Peripheral Module
A. Mechanical Structure and Power Management
The mechanical structure is welded by high-strength
stainless steel to protect users, which includes:
■ A heavy chassis with a strong and wear-resistant
structure, which is able to adjust the height to tailor
the user's habits.
■ An efficient motor providing strong power and a
set of general current limiting resistance limiting
the speed to guarantee safety.
■ A 24V, 20Ah lithium-ion battery which ensures at
least six hours of movement, completely satisfying
outdoor activities.
Figure 4. Overview of the multi-sensor control system.
xy:
x: Left Eye 0: Open Eye
y: Right Eye 1: Closed Eye
01/10
Advance
00/11
01/10
Brake
Figure 5. Flow chart of the wheelchair control logic.
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IEEE CIRCUITS AND SYSTEMS MAGAZINE
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B. Communication Module
A Wi-Fi Customer Premise Equipment (CPE) is deployed
to provide wireless communication, which feeds back
the WSI to the phone or computer in time. When the
wheelchair rolls over, malfunctions, or meets an emergency,
the system will call the preset contact, through
VoIP telephony by Skype.
C. Display Module
The screen consists of two main parts:
■ Virtual Screen: As the receiver of eye movements,
the transparent screen in front of the user can be
2The basic classes in C# are displayed on the website of Tobii as http://
developer.tobiipro.com/unity/unity-sdk-reference-guide.html.
THIRD QUARTER 2021
and SB
are included. Steering is realized
http://developer.tobiipro.com/unity/unity-sdk-reference-guide.html http://developer.tobiipro.com/unity/unity-sdk-reference-guide.html
IEEE Circuits and Systems Magazine - Q3 2021

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