Authors: Yeh-Liang Hsu, Po-Er Hsu, Yi-Shin Chen (2010-08-21);
recommended: Yeh-Liang Hsu (2010-08-21).
Note: This paper is presented at the 25th World Electric
Vehicle Symposium and Exposition (EVS 25), Nov 5-9, 2010, Shenzhen, China.
Development of an intelligent robotic wheelchair as the center
of mobility, everyday living, and healthcare of the senior users
describe the design concept and current progress of an intelligent robotic
wheelchair (iRW) developed at he Gerontechnology
Research Center of Yuan Ze University, Taiwan, which intends to redefine the
wheelchair as the center of mobility, everyday living and healthcare of the
senior users. Centered on the needs of the senior users, the core of the iRW is a user interface designed
specifically for the senior users’ declining ability in perception, motor
control and cognition. The iRW is
composed of a moving vehicle, a sensing and control module, and an information/communication
module, to provide the senior users three types of functions: mobility,
everyday living, and healthcare. The iRW
is expected to assist the senior users to interact with the environment more
effectively, including physical interaction, environmental control, information
exchange, and most importantly, interpersonal communication. The final aim is
to enhance independence and social participation, and to improve the quality of
life of the senior users.
Keywords: robotic wheelchair,
Mecanum wheel, indoor navigation, home telehealth system, Stewart platform.
aging society has brought an increasing demand in living support and healthcare.
Social participation of the elderly people is also becoming an issue of
increasingly concern. Lower limb disability is one of the most common disabilities among
elders, and wheelchair is the most common and important mobility aids. Electrical wheelchair is an option for senior users who cannot move
themselves on a wheelchair. However, operating an electrical wheelchair is often
difficult for senior users. Fehr et al.  surveyed 200 people with severe
disabilities who were trained for operating electrical wheelchairs. Ten
percent of the testers thought electrical wheelchairs cannot satisfy their living
requirement and 40 percent could not use electrical wheelchairs to
move to where they wanted. Although this survey is for disable people, the
usability of electrical wheelchairs can also a major problem for senior users.
In recent years, research in electrical wheelchairs
has been emphasizing on how to implement the sensing and judgment capabilities
commonly seen on robots, so that the wheelchairs can perform autonomous
behaviors to a certain extent in order to improve its
usability. Miller and
Slack  first used the term “robotic wheelchair” in their research. They applied
various sensing and navigation technologies that are often used in robotics and
built two prototypes of robotic wheelchairs, which were able to assist users to
pass through narrow paths and avoid obstacles.
is one of the major research issues in robotic wheelchair, since mobility assist
is the fundamental function of a wheelchair. Prassler et al.  developed
robotic wheelchair MAid (Mobility Aid for Elderly and Disabled People) to
support and transport senior users with limited motion skills and to provide
them with a certain amount of autonomy and independence. As shown in Figure 1,
in a test, MAid could travel autonomously in the concourse of a railway station
through crowded people.
1. Robotic wheelchair MAid, traveling in the concourse of a railway station 
navigation, man-machine collaborative control scheme is also a very important
issue of the research of robotic wheelchair [4, 5]. Galindo et al. 
developed a robotic wheelchair SENA to facilitate mobility of the disable
people and senior users. They considered completely autonomous performance of a
mobile robot within non-controlled and dynamic environments is not possible
yet, due to different reasons including environment uncertainty, sensor/software
robustness, limited robotic abilities, etc. They presented the design and
implementation of the human-robot-integration idea into SENA, which permits a
person to extend/improve the autonomy of the whole system by participating at
all levels of the robot operation, from deliberating a plan to executing and
controlling it. Figure 2 shows the execution of navigation tasks from
interactions between human and robotic wheelchair
Figure 2. Executions of navigation tasks from
interactions between human and robotic wheelchair 
Agostini  considered collaboration between the users and robotic wheelchairs
will improve the efficiency of navigation tasks. They classified the
collaborative relationship into behavior model, man supervisor, and robot
supervisor, and implemented the collaborative control strategy in their robotic
wheelchair VAHM. Takahashi et al.  developed a robotic wheelchair in which
the user can use body posture to control forward/backward motion by sensing the
change of user’s center of gravity (Figure 3). Katsura et al.  combined the
capability of the user and the robotic wheelchair to design the collaborative
scheme to reduce the operational load for the user.
Figure 3. Use the change of user’s center of
gravity to control robotic wheelchair forward/backward 
elderly people living in nursing home or in the home environment, the wheelchair
is the place where they spend the most time in everyday living for many senior
users. In addition to providing mobility assistance, the wheelchair should also
integrate and satisfy the needs in everyday living, healthcare, and social
describes the design concepts and current progress of an on-going research
project conducted in the Gerontechnology Research Center in Yuan Ze University,
Taiwan, in constructing an intelligent robotic wheelchair (iRW), which intends to redefine the
wheelchair as the center of mobility, everyday living and healthcare of the senior
users, based on the concept of robotic wheelchairs. Figure 4 describes
the overall design concept of the iRW
developed in the study. Centered on the needs of
the senior users, the core of the iRW is a user interface designed
specifically for the senior users’ declining ability
in perception, motor control and cognition, a moving vehicle. The iRW is composed of a moving vehicle, a sensing
and control module, and an information/communication module, to provide the senior
users three types of functions: mobility, everyday
living, and healthcare. The iRW is expected to assist the senior users to interact with the
environment more effectively, including physical interaction, environmental
control, information exchange, and most importantly, interpersonal
communication. The final aim is to enhance independence and social
participation, and to improve the quality of life of the senior users.
Figure 4. Design concept
of the iRW
2. Design concept of
The iRW is
currently in the prototyping stage. The functions planned for the iRW are described as follows:
The iRW is designed for home or nursing home
use, to be used mostly indoor or short-distance outdoor (such as taking a walk
in the garden). The iRW employs a Mecanum-wheeled vehicle
which can move in any direction for nimble maneuver. The iRW also
shows autonomous behaviors by implementing functions such as the indoor
navigation, obstacle avoidance, and dynamic route planning. Schemes of collaborative
control are also developed to make the iRW more convenient and easy to use in
home and nursing home environments.
(2) Everyday living
The iRW uses the concept of Stewart platform
to design a versatile seat mechanism with multiple degrees of freedom in seat
adjustments to provide transfer assist and comfortable seating positions to the
senior user to handle the various situations encountered in everyday living. Interacting
with the wireless sensor network constructed in the home or nursing home environment,
the iRW provides the senior user with convenient environmental
information and communication module in the form of a digital photo frame embedded
in iRW also provides a channel of information exchange and
interpersonal communication for the senior user.
The iRW provides an easy-to-wear, non-invasive
device for blood oxygenation measurement. Other physiological signals such as
heart rate and respiration rate can be derived for real time monitoring of the
signs of life. Combining with the information and communication module, a home
telehealth system is also achieved on the iRW.
Figure 5 is the appearance planned for the iRW. The
current progress of the various systems of iRW
will be described in the next section.
Appearance planned for the iRW
assistance is the basic function of the robotic wheelchair. Nimble
maneuverability is of the highest priority for the iRW to be used in the crowded indoor home environment. For this
reason, the moving vehicle of the iRW
uses 4 Mecanum-wheels, which was designed by Swiss inventor Bengt Ilon. As
shown in Figure 6, the outer ring of the Mecanum wheel has free rollers in a 45
degree angle with the wheel’s axis. The vehicle can move in all directions by
controlling the direction of rotation of the 4 Mecanum wheels.
have been used in electrical wheelchairs, as shown in Figure 6. In our design,
the moving vehicle of iRW can go
forward/backward, shift right/left, and rotate clockwise/counterclockwise by controlling
Figure 6. The Mecanum wheel and application [http://car.pege.org/2006-ever-monaco/wheel-chair.htm]
We did not
implement complete automatic navigation function in the iRW because it is too costly to be practical to achieve the
required accuracy. Instead, a semi-autonomous indoor navigation using landmarks
is implemented using the concept similar to the automated guided vehicles (AGV)
to reduce the operation load of senior users. Landmarks are deployed on the
ceilings as “virtual AGV track”. When iRW
is steered under a landmark and a camera on the iRW catches and identifies the landmark, the iRW can then interpret the information contained in the landmark
and follow the virtual AGV track to move to the specific location, such as bed
room, living room, kitchen, etc.
indoor navigation system is low cost, flexible, and easy to implement. The QR code
(Quick Response code), which is a two-dimensional bar code system commonly used
in various applications, is used as to generate the landmarks in this system.
There are many software programs for generating and recognizing QR code. The
user can generate and print out the QR code landmarks and easily deploy the
virtual AGV track in the home environment. For example, Figure 7 shows “bedroom”
and “kitchen” in QR code. In addition, ultrasonic range-finding sensors are
used to perform the low cost and reliable function of obstacle avoidance. When
an obstacle is detected within a specific distance from the iRW, iRW
simply stops all autonomous behaviors and handed the control to the user.
Figure 7. “Bed room” and “kitchen” in QR code
Seat adjustment mechanism
The iRW uses the concept of Stewart platform
to design a versatile seat mechanism with multiple degrees of freedom in seat
adjustments needed in various situations encountered in everyday living,
including comfortable seating positions and transfer assists from wheelchair to
bed, toilet, etc.
is a parallel structure robot which has the advantages of high stiffness and
high positioning accuracy compared to the serial structure robots. The geometry
of this parallel robot, illustrated in Figure 8, is composed of a fixed base, a
movable platform, and 6 variable length actuators connecting the fixed base and
the movable platform. This is a 6 degrees-of-freedom
universal-prismatic-spherical mechanism, including heave, surge, sway, yaw,
pitch, and roll.
Figure 8. Schematic diagram and degrees-of-freedom
of parallel robot
required in transfer assist and comfortable seating positions, the seat
mechanism of iRW needs only 4 degrees-of-freedom
which are heave, surge, sway, and pitch. As shown in the conceptual sketch in Figure
9, the seat mechanism of iRW uses a four-axis Stewart platform. In
this design concept, the Mecanum-wheeled vehicle is the fixed plate, while the
seat is the movable plate of Stewart platform. Based on this design concept,
the prototype of the iRW is developed
(Figure 10). In order to enhance the stability of the seat, a locking-mechanism
is designed to constrained uncontrolled degree of freedoms (surge and sway) of
the seat. Table 1 shows the functions and specifications of the seat adjustment
Figure 9. Design concept of the seat adjustment
mechanism of iRW
Figure 10. Prototype of the iRW
Table 1. Functions and specifications of the iRW
Adjustment of comfort
Height of the seat
(Distance from the bottom of the seat to the
Highest position: 498mm
Initial position: 433mm
Lowest position: 368mm
Adjustment of assistance
Back/hip pressure variability
+15° ~ -15°(Pitch)
Home telehealth system
telehealth system of the iRW is in
the form of a “Care Delivery Frame (CDF)”. CDF integrates two distinctly
different applications, the home telehealth system and the remote photo sharing
service of digital photo frame, to create a unique information channel for
senior users who are not familiar with the operation of computers and Internet.
In addition to health data monitoring, children or caregivers can “deliver
care” to their seniors not living together by warm messages and thoughtful reminders
on the CDF, as well as sharing their feelings, joy, and life experience through
photos and video clips. Even more applications can be imagined once this
information channel to the seniors at home is established, such as
entertainment, displaying life information or even commercial ads. As shown in
Figure 11, CDF provides the following 4 main functions:
function of CDF is the Distributed Data Server (DDS) of the decentralized home
telehealth system . All technical functions of a home telehealth system are
built in the CDF. Currently the vital sign sensors that can be connected to CDF
are blood pressure meter, blood glucose meter, and blood oxygenation sensor.
Remote photo sharing
provides a platform for children and caregivers to upload photos and videos
clips remotely, and to manage the display sequence and timing on the CDF for
their seniors not living together.
Caring messages and reminders
can send warm caring messages and thoughtful reminders to their seniors to
display on the CDF.
Entertainment and life information
with information service companies, CDF can also be a platform to display
information such as weather, shopping, as well as music and other entertainment
Figure 11. The 4 main functions of the Care
The CDF software is running independely on a “pad PC”,
which can be installed and seperated from the iRW when the senior user leaves the iRW. Figure 12 shows the management pages
of the 4 main functions for CDF.
Figure 12. Management pages of the 4 main functions for CDF
Figure 13 shows
photos of the first prototype of iRW
developed in this project, which is in a skeleton form constructed by aluminum
extrusions. This prototype is currently under intensive testing for functions.
Human factor evaluations and industrial design are also being carried out.
After the functional tests are completed, a field test of the iRW will be conducted in a nursing home
to get feed back from the senior users and further improve its usability.
Figure 13. Photos of the first prototype of iRW
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