Authors: Po-Er Hsu, Yeh-Liang Hsu, Jun-Ming Lu, Jerry, J.-H. Tsai, Yi-Shin
Chen (2011-05-21); recommended: Yeh-Liang Hsu (2011-05-21).
Note: This paper is presented in the “1st Asia Pacific eCare
and TeleCare Congress,” June 16-19, 2011, Hong Kong, China.
iRW: An Intelligent Robotic Wheelchair Integrated with Advanced Robotic
and Telehealth Solutions
With the global
trend of aging, there has been a growing demand for human-friendly wheelchairs
as mobility aids. In addition to the enhanced mobility and more comfortable use,
people also expect a wheelchair to be the center of everyday living and health
care. This paper describes the development of an intelligent robotic wheelchair
(iRW) which integrates with advanced robotic
and telehealth solutions. While most technologies required are readily
available, the emphasis in this research is to properly adapt and integrate these
technologies into the iRW to make it
human desirable and business viable.
requests of senior users and professional caregivers, the design needs of the iRW were defined. Various technologies
were reviewed for the possibility of meeting those needs. The iRW is composed of a moving vehicle, the
sensing/control module and the information/communication module to provide mobility
aids and supports for everyday living and healthcare. Integrated with Mecanum
wheels, the sensing/control module and a simplified indoor navigation system, the
senior user can freely control the wheelchair in all directions or let the
wheelchair move from site to site automatically. Besides, the Stewart platform
with reduced degree-of-freedom and the ergonomically designed seat integrated
with pressure sensors enable relaxed sitting with dynamic postures, as well as
lifting and transfer assistance. Moreover, the telehealth system in the form of
a digital photo frame serves as the platform of health care management and the
information channel between the wheelchair user and the family or caregivers.
adapting the robotic and telehealth solutions, the iRW realizes enhanced mobility, improved safety and comfort, better
environmental control, enriched information exchange, and stronger interpersonal
communication. The iRW has good
potential to help the senior user interact with the home environment more
effectively and actively, while improving the quality of life of the elderly
Keyword: robotic wheelchair, indoor
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 users who cannot move themselves on a wheelchair. However, operating
an electrical wheelchair is often difficult for 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 be 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 often used in robotics and built two prototypes of robotic
wheelchairs, which were able to assist users to pass through narrow paths while
navigation 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 users with limited motion skills and to
provide them with a certain amount of autonomy and independence.
collaborative control scheme is another important issue in the research of the robotic
wheelchair [Katsura and Ohnishi,
2004; Galindo et al., 2006a]. Galindo et al. [2006b] developed a robotic
wheelchair SENA to facilitate mobility of the disable people and 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
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. 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.
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. Mobility is one of the fundamental requirements of the quality of
life to senior users. In addition to providing mobility assistance, the
wheelchair should also integrate and satisfy the needs in everyday living,
healthcare, and social participation.
With the global
trend of aging, there has been a growing demand for human-friendly wheelchairs
as mobility aids. In addition to the enhanced mobility and more comfortable
use, people also expect a wheelchair to be the center of everyday living and
health care. This paper describes the development of an intelligent robotic
wheelchair (iRW) which integrates
with advanced robotic and telehealth solutions. While most technologies
required are readily available, the emphasis in this research is to properly
adapt and integrate these technologies into the iRW to make it human desirable and business viable.
Section 2 of the
paper describes the needs and design concept of the iRW. Section 3, 4, and 5 describe technologies to achieve the
functions in mobility, everyday living, and health care of the iRW, with emphasis on the discussion on
how technologies be best used to support the needs. Finally Section 6 concludes
The needs and design concept of
The iRW intends to redefine the wheelchair
as the center of mobility, everyday living and healthcare of the senior users,
based on the technologies of robotic wheelchairs. Figure 1 describes the
overall design concept of the iRW developed
in this 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. The iRW is composed of a moving vehicle, a sensing/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 1. Design concept of the iRW
In addition to
the technical development, the design process of the iRW focused on answering the question: “How can technology be best
used to support the needs of the aging society?” Following the “Design
Thinking” proposed by IDEO CEO Tim Brown (Figure 2), the development of the iRW continuously
focused on the simultaneous consideration of “human desirable, business viable,
and technology feasible”.
Figure 2. Design
thinking [IDEO (http://www.ideo.com) CEO Tim Brown]
Figure 3 is the
fishbone diagram of technologies used in the iRW. The needs collected in interviews with 17
experts and professional caregivers and questionnaires from 403 senior users were
classified into needs in mobility, healthcare and everyday living. To answer
the major needs, an animation movie of the iRW
was made to describe the application scenario of the iRW. The animation movie was also used to confirm with the experts
and professional caregivers on the application scenario of the iRW. Technical functions to be achieved
were then identified.
Figure 3. The fishbone diagram of technologies of
After these technical functions were defined,
various technologies were reviewed for the possibility of meeting those technical
functions. At this stage, the major consideration is whether the technologies are
“business viable” on the iRW, such as
the cost, reliability, and usability of the technology. The detail of technologies
selected is described in the following sections.
Technologies for mobility functions
of the iRW
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). Referring to Figure 3, nimble maneuver is required for the iRW should be able to move freely in
home and nursing home environments. Autonomous behaviors are needed to reduce
the operating load of the senior users.
Schemes of collaborative control also need to be developed to make the iRW more convenient and easy to operate.
Most electrical wheelchairs are two-wheel drive, and cannot move
sideways. Figure 4 shows the Mecanum-wheeled
vehicle of the iRW for nimble maneuver in all directions. The 4 Mecanum wheels and motors are
installed at the corners of the chassis. The outer ring of every Mecanum wheel
has free rollers, which make a 45 degree angle with the wheel’s axis. A
joystick controller is used to control the iRW
to move forward/backward, sway right/left, and spin clockwise/counter
clockwise. Table 1 shows the specifications of Mecanum wheeled vehicle of the iRW.
The maximum forward speed of the iRW is
set at 3km/h, which is close to walking speed of human, and the maximum backward
and sideways speed is set at 1.5km/h.
Figure 4. Mecanum wheeled of the iRW
Table 1. Specifications of the Mecanum wheels and
motors of the iRW
3 km/h (Max)
Backward, sideways, clockwise/counter clockwise
Voltage/Current of the motor
24V/3 (A, Max)
24V, 9.6Ah, 402×133.5×71.5 (L×W×H, mm), 3.4 kg
navigation can be achieved by processing the “received signal strength
indicator (RSSI)” from a carefully-designed wireless sensor network. We chose
not to use this technology in the iRW
because it is too costly to be practical to achieve the required navigation accuracy.
Instead, a semi-autonomous indoor navigation is implemented using the concept
similar to the automated guided vehicles (AGV) to reduce the operation load of
AGV is a mature
technology which can follow the physical guide-paths and have the intelligence to
perform actions. Early the guide-paths
of the AGV were installed in the floor, and hence, some variants installed the guide-paths
on the ceiling to reduce the floor modification and cost [Vis, 2006]. For the iRW, QR code
(Quick Response code) landmarks are deployed on the ceilings as “virtual AGV
track”. When the iRW is steered under
the track, the camera on the iRW will
capture and recognize the QR code. Subsequently, the information conveyed by
the QR code can be interpreted so that the iRW
follows the virtual AGV track to move to the specific stop, such as bed room,
living room, kitchen, etc. The user then takes over to steer the iRW to the required location.
indoor navigation system aims to reduce the operating load of steering the iRW manually on a long path. It is
inexpensive, flexible, and easy to implement. The QR code is a two-dimensional
bar code system commonly used in various applications. Public domain software
programs are available for generating and recognizing QR codes. The user can
generate and print out the QR code landmarks and easily deploy the virtual AGV
track in the home environment.
The camera installed on the iRW can also be used for tele-operation.
Remote operator can help move the iRW
when necessary. In addition, low-cost and reliable ultrasonic range-finding
sensors are used to perform obstacle avoidance function in the iRW. When an obstacle is detected within
a specific distance from the iRW, iRW simply stops all autonomous
behaviors and handed the control back to the senior user. Advanced control
interface such as voice control was considered in the development process. But
we decided to stick with the traditional joystick and buttons to reduce the complexity
of the control.
Technologies for everyday
living functions of the iRW
Figure 3, multiple degree-of-freedom (DOF) seat adjustment is required in the iRW to provide transfer assist and
comfortable seating positions for various situations encountered in everyday
living. The seat itself serves as the interface between the senior user and the
iRW. Ergonomic seat design is also important
for the senior user to sit on the iRW
for a long period every day.
is a parallel robot which has advantages of high rigidity and high positioning
accuracy comparing with the serial structure robots. The Stewart platform (Figure
5) is composed of a fixed base, a movable platform, and 6 variable length
actuators connecting the fixed base and the movable platform. This is
universal-prismatic-spherical mechanism has 6 DOFs, including heave, surge,
sway, yaw, pitch, and roll.
On the iRW, a 4-axis Stewart platform is
implemented to provide multiple DOF seat adjustment. Figure 6 shows the
design concept of the seat adjustment mechanism integrating with the
Macanum-wheeled vehicle of the iRW.
As shown in Figure 6, the seat plate is the movable plate of the Stewart
platform, and the L-shape structure of the chassis is the fixed plate of the Stewart platform. The number of variable
length actuators is reduced from 6 to 4 because only 4 degrees of freedom,
heave, surge, sway and pitch, are required for height adjustment, transfer
assist, and sit-stand assist. Note that two variable length actuators are in
tension and the other two are in compression. These variable length actuators
also serve as structural members of the iRW.
In order to increase the stability and safety, locking mechanism is designed to
constrain the uncontrolled DOF, surge and sway of the seat. Table 2 shows specifications of the seat adjustment.
Figure 5. Stewart platform
Figure 6. 4-axis Stewart platform is implemented on the
Table 2. Specifications of the seat adjustment mechanism
Thrust force/ Self-locking force of the variable length actuator
Stroke of the variable length actuator
Current of the variable length actuator
2.5 (A, Max)
460 ~ 345 mm
20° ~ -8°
A standard ergonomic seat design process was
carried out to establish the dimensions and shape of the seat by referencing to
the Anthropometric Data Book of people in Taiwan [Wang et al., 2002] and the
human spine contour. However, in the prototyping stage, we decided to directly
install a seat made by memory foam seat from an existing chair, considering the
cost of fabricating a new seat. The memory foam can help relieve the body
pressure for better comfort. The armrests are redesigned to be adjustable in
height during transfer assist. Table 3 shows dimensions of the seat and
Table 3. Dimensions of the seat
Width of the seat
Length of the seat
Height of the seat back
Height of the armrest
0 ~ 200 mm
Width of the armrest
Length of the armrest
Technologies for the healthcare
functions of the iRW
Figure 3, the iRW should provide a
telehealth system with easy-to-wear, non-invasive devices for real time vital
sign monitoring and long-term health care management for the senior users,
their family and caregivers. In addition, function of preventing pressure ulcer
is also important for the senior users who sit on the iRW for a long period of time every day.
telehealth system of the iRW is in
the form of a “Care Delivery Frame (CDF)” (Figure 7). By integrating the home
telehealth system and the remote photo sharing function of a digital photo
frame, the iRW aims to create a
unique information channel for senior users who are not familiar with the
computers and the Internet. In addition to the monitoring of health status,
children or caregivers can deliver care to the elderly with warm messages and
thoughtful reminders displayed on the CDF. Further, they can share their
feelings, joy, and life experience with the elderly by means of digital photos
and video clips. Moreover, the daily news, weather information, and even
commercial ads can be provided through the use of the CDF. The CDF software is
running independently on a pad PC, which can be installed and separated from
the iRW when the senior user leaves
the iRW. The four main functions of the
CDF are described below:
function of CDF is based on the Distributed Data Server (DDS) of the
decentralized home telehealth system [Hsu, 2007]. All technical functions of a
home telehealth system are built in the CDF. Currently the vital sign sensors
that can be connected to the CDF include the sphygmomanometer, the blood
glucose meter, and the oximeter (for real time vital sign monitoring).
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
the senior users who are not living together with them.
Caring messages and reminders
and caregivers can send warm caring messages and thoughtful reminders displayed
on the CDF to the elderly.
Entertainment and life information
with information service companies, CDF can also be a platform to display
information such as weather forecast and shopping discounts, as well as music
and other entertainment information.
Figure 7. The four main functions of the Care
Delivery Frame (CDF)
implemented on the seat of the iRW to
sense the pressure during the senior user sitting on the iRW. Smartpad is a soft, comfortable, washable and low-cost
pressure sensing unit. The structure of Smartpad is the multi-layers
architecture which is composed of elastic fabric, conductive fabric, and foam. There
is a linear relationship between the pressure and the resistance of the sensor pressure
is applied on SmartPad. If the pressure
distribution does not change in a while, the iRW will adjust the seating position to relieve the pressure
to prevent pressure ulcer by controlling the 4-axis Stewart platform.
describes the development of an intelligent robotic wheelchair intending to redefine
the wheelchair as the center of mobility, everyday living and healthcare of the
senior users, based on the technologies of robotic wheelchairs. In addition to
the technical development, the design process of the iRW focused on answering the question: “How can technology be best
used to support the needs of the aging society?”
Figure 8 shows
the first and second lab prototypes of the iRW.
The first prototype is for realization of the various functions. Currently the
second prototype is under user evaluation. By carefully adapting the robotic
and telehealth solutions, the iRW realizes
enhanced mobility, improved safety and comfort, better environmental control, enriched
information exchange, and stronger interpersonal communication. The iRW has good potential to help the senior
user interact with the home environment more effectively and actively, while
improving the quality of life of the elderly people.
Figure 8. The prototypes of the iRW
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