Authors：Po-Er Hsu (2013-01-28);
recommended: Yeh-Liang Hsu (2013-02-10).
Note: This article is the Chapter 1 of Po-Er Hsu’s doctoral thesis
“Development of an intelligent robotic wheelchair as the center of mobility,
health care, and daily living of older adults.”
Chapter 1. Introduction
Over the past
decades, the rapidly aging society has brought an increasing demand for living
support and healthcare. The ageing process of older adults results in declined
functional status and decreased mobility, which affects their level of
self-care and independence. Mobility is a crucial aspect regarding one’s living
independence. It is sensitive to changes in health and psychological status and
is one of the most crucial factors determining one’s functional capacity [Celler
et al., 1995; Heikkinen, 1998]. Limited mobility is associated with a
deterioration of health and functional impairment in older adults [Folden et
mobility, people with disability frequently employ mobility assistive
technology (MAT) such as canes, walkers, manual wheelchairs (MWCs), power
wheelchairs (PWCs), and scooters, etc [Souza et al., 2010]. Many older adults who have multiple and complex physical
and cognitive impairments use wheelchairs as a primary means of mobility [Wang,
2011]. A wheelchair is the most common and important aid for older adults. Nineteen
percent of older adults 65 years or older use wheelchairs, and they are the majority
(57.5 percent) of manual wheelchair users [NCHS, 2004]. Moreover, approximately
50 percent of older adults in Canadian institutions use wheelchairs for
mobility [Shields, 2004].
This chapter first
discusses the design issues in mobility assistance and seat adjustment of the
wheelchair. A patent analysis is also presented to explore the current trend of
power wheelchair development. The emerging field of “robotic wheelchair” is
then introduced. Finally, the purpose of this research, to develop an
intelligent robotic wheelchair for older adults, is presented.
1.1 Design issues in mobility assistance of the wheelchair
transportation devices, movement of the wheelchair is slow, short, and is
discontinuous. Sonenblum et al.  collected 25 non-ambulatory, full-time
power wheelchair users’ wheelchair usage data in 395 days. They found that the users
spent 10.8 ± 2.9 hours
daily sitting on the wheelchair, and they moved the wheelchair in less than ten
percent of the time. The median of “mobility bouts” which is used to represent
transition numbers between activities was 110 times a day. Tolerico et al.
 studied the usage of manual wheelchairs for daily living in the home.
They concluded that wheelchair users spent 8.3 ± 3.3 hours daily sitting on the
wheelchair, and the average operating speed was 0.79 ± 0.19 m/s. The maxima
period and distance of continued movement were 2.9 ± 1.4 min and 215.6 ± 119.8
m. Many other researches on wheelchair usage had similar findings, as
summarized in Table 1-1.
Table 1-1. The survey of researches of the
et al. 
et al. 
et al. 
Sonenblum et al.
Karmarkar et al. 
26 / 13
(MWC / PWC)
46.8 ± 13.3
62.5±5.7 / 66.9±7.5
(MWC / PWC)
8.3 ± 3.3
10.8 ± 2.9
0.44 ± 0.09
0.79 ± 0.19
0.64 ± 0.13 / 0.7 ± 0.3
(MWC / PWC)
period of continued movement
2.9 ± 1.4
2.5 ± 1.9 /
4.2 ± 2.8
(MWC / PWC)
of continued movement
215.6 ± 119.8
± 190.4 / 344.1 ± 324.9
(MWC / PWC)
PWC / Home
MWC / Home
MWC / Home
Older adults with difficulties self-propelling manual wheelchairs,
which can be attributed to physical capacity declined or overexertion, may benefit
from power wheelchairs [Curtis et al., 1999; Algood et al., 2005]. However, the
maneuverability and accessibility of power wheelchairs can also be a major
problem for older adults.
About one third
of wheelchair and scooter users reported that they have accessibility problems
outside the home in a survey of wheeled mobility devices usage in the United
States [Kaye et al., 2000]. The wheelchair users often expressed problems
related to environmental access (e.g., door widths and passageways that are too
narrow, inaccessible bathrooms, obstructed travel, and transportation) and the
hardware of manual/power wheelchairs (e.g., manual wheelchairs that are too
heavy to push or maneuver and power wheelchairs that are too wide or
complicated to use) [Berry et al., 1996; Meyers et al., 2002; Chaves et al.,
2004]. Fehr et al.  surveyed 200 practicing clinicians in a variety of
clinics, residential treatment facilities, and rehabilitation hospitals. Forty
percent of the patients who received power wheelchair training thought that the
power wheelchair was difficult or impossible to maneuver. Nearly half of the
patients unable to control a power wheelchair by conventional methods would
benefit from an automated navigation system, according to their clinicians.
Further, Koontz et al.  used four maneuverability trials, as shown in Figure
1-1, to evaluate 109 manual wheelchairs, 89 power wheelchairs, and 15 scooters recently.
They concluded that many wheelchairs were unable to access the public place where
the turning space was limited. They suggested that revision of the ADAAG
guidelines was necessary to improve access to a space within the built
Figure 1-1. Four maneuverability trials
1.2 Design issues in seat adjustment of the wheelchair
In addition to
providing mobility assistance, seat adjustment design
is of crucial importance in a wheelchair. The wheelchair user makes direct
contact with the seat, which serves as the interface between the user and the
wheelchair, for much of a given day. Souza et al.  examined 50 journal
articles on mobility assistive technology (MAT) and concluded that electric
wheelchairs should be considered not only as providing mobility for advanced
stages but as mobility assistive technology that can be integrated with an adjustable
seating system to reduce fatigue.
functional independence for older adults who use a wheelchair, their posture
and comfort should be considered. Redford  reviewed studies specifically
concerned with seating and wheeled mobility for older adults, and concluded
that these users would benefit from matching of mobility to function, cheaper
and more effective cushions, more modular seating systems, and better lifting
and transfer. Among the considerations in wheelchair seat design, pressure
management received the most attention. Sitting-acquired pressure ulcers are a
significant healthcare problem for wheelchair users. Various seating designs
have been proposed for maintaining tissue viability
while the user is in the wheelchair. For example, air cells with pressure
sensors to monitor the pressure distribution on the buttock are often utilized
to provide timely adjustment of the shape of the seat cushion to relieve
concentrated pressure [Henderson et al., 1994; Burns and Betz, 1999; Chugo et
al., 2011]. “Dynamic seating” on the wheelchair, in which a power-operated seat
adjustment mechanism would allow the user to maintain proper posture, was also
proposed [Graf et al., 1995].
backrest recline, and seat elevation are the most clinician-prescribed seat
adjustment functions of electric wheelchairs to facilitate posture change
and/or assist activities of daily living (ADL) for users [Paralyzed Veterans of
America, 2000; Trefler et al., 2001]. Ding et al.  surveyed the real-life
usage of powered seating functions among wheelchair users during their daily
activities. Results showed that subjects accessed tilt-in-space, backrest
recline, and seat elevation 19 ± 14 times, 12 ± 8 times, and 4 ± 4 times per
day, respectively. Further, of the time participants spent in a wheelchair,
39.3% ± 36.5% was in the tilted or reclined positions. Lacoste et al.  interviewed
40 participants at home and reported that 97.5 percent used the powered
tilt-in-space and/or recline function in a given day and that 70 percent used the
functions primarily to rest, relax, increase comfort, and decrease pain.
have been conducted to evaluate seat pressures at different angles of the
tilt-in-space function in laboratory settings. Sprigle et al.  found that
the tilt-in-space function reduced static seating pressure significantly, which
was a key factor in pressure ulcer prevention. In addition, many
laboratory-based studies suggested that large tilt-in-space angles can be used
to manage seating pressure to reduce the risk of pressure ulcers [Henderson et
al., 1994; Stinson et al., 2002]. Aissaoui et al.  concluded that the
maximum pressure reduction at ischial tuberosities was at 45° of tilt-in-space.
In addition to
providing seating comfort and pressure management, the seat elevation function for
wheelchair users is considered medically necessary [Cooper et al., 2004; RESNA,
2005]. The seat elevation feature can help wheelchair users accomplish
mobility-related ADL, such as performing transfers and reaching objects at
different heights to preserve upper-limb functions and to achieve eye contact
in social situations.
A search of
related patents indicated that most seat adjustment functions for wheelchairs applied
linkage mechanisms [Cerreto et al., 2012; Chuang, 2011; Wu et al., 2009].
Additionally, some linkage mechanisms were implemented with actuators or motors
to provide multiple degrees of freedom (DOF) in seat adjustment. Bae and Moon
 designed a wheelchair seat mechanism, as shown in Figure 1-2, using four
actuators to achieve the forward/backward tilting, elevation, and standing
motions. The seat mechanism is composed of four independent adjustment
mechanisms, each of which is driven by an actuator. Wada  used a linear
drive unit to develop a chair tilting system for the climbing wheelchair to maintain
the angle between the seat and the floor. Lee et al.  developed a seat
adjustment mechanism that is integrated with the frame of the wheelchair to increase
stability by shifting the center of gravity. The mechanism also provided a
tilt-in-space function. Koontz et al.  evaluated 109 manual wheelchairs,
89 electric wheelchairs, and 15 scooters for maneuverability. They concluded
that the angles produced by the tilt-in-space and recline functions lengthen electric
wheelchairs and therefore increase the space needed for maneuvering. Weight and
complexity of the wheelchair is also increased with the multiple-DOF seat
Figure 1-2. Wheelchair seat mechanism
activities mainly determine the degree of independence attainable by wheelchair
users in daily living. Among all transfer activities, sitting pivot transfer
(SPT) is the most commonly used [Finley et al., 2005; Perry et al., 1996; Bromley,
1998; Somers, 2001]. The basic steps of SPT are moving the buttocks toward the
edge of the initial surface, placing the feet in a stable position, and leaving
one hand on the initial surface (trailing) while placing the other hand on the
target surface (leading). The arms are used to push up from the initial surface
and pivot the body on the feet, swinging and landing the buttocks onto the
target surface [Koontz et al., 2011]. However, proper transfer technique may
not be sufficient when wheelchair users encounter height differences and gap
crossing between wheelchair and target surface [Forslund et al., 2006].
Few studies have
examined the development of a transfer assist function of a wheelchair. Khatchadourian
et al.  used robotic technologies to develop a mobile robot molded into a
forklift for users to perform transfer activities. The user uses a beacon to position
the mobile robot close to him or her. Then, the user can apply force to the
support arms of the lifting mechanism to relocate himself or herself into the mobile
robot to finish the transfer activities. Bostelman and Albus  built a “Home
Lift, Position and Rehabilitation (HLPR) Chair”, as shown in Figure 1-3, to provide
independent mobility and transfer activities assist for the user in the indoor
environment. However, the size (1,450×580×1,780 mm in mobility
configuration, 1,450×580×2,410 mm in full
lifted configuration) and weight (136 kg) of the HLPR chair may make it impractical for the home.
Figure 1-3. Home Lift, Position and Rehabilitation
A patent search
from the United States Patent and Trademark Office (USPTO) database is conducted
to explore the current trend of power wheelchair development. Using “wheelchair”,
“electric”, “power” and “motor” as the key words, 637 patents were retrieved. Table
1-2 summarizes the patent search strategy. The complete patent analysis (in
Chinese) is in Appendix.
Table 1-2. Patent search strategy
The United States
1976/01/01 to 2012/07/01
ICL/A61$ AND ABST/((power$ OR electric$) OR
motor) AND wheelchair
Figure 1-4 shows
the technology life cycle (TLC) based on the patent and assignee number. The
TLC can be used to analyze the technological development phase. There are four phases: “research and development phase”, “ascent
phase”, “maturity phase”, and “decline phase”. Figure 1-5 is the technology
life cycle drawn from the power wheelchair patents in USPTO. Comparing Figure
1-5 with Figure 1-4, the technological development of
the power wheelchair is in the decline phase.
Figure 1-4. Technology life cycle (TLC) of the
Figure 1-5. Technology life cycle of the United
Patent Classification (IPC) is used to classify the patents according to
different technologies. Table 1-3 lists the top five IPCs among all patents in power
wheelchairs. Note that a patent may belongs to more than one IPC. From this IPC
ranking, technology development of power wheelchair focuses on motors, parts
and accessories, and facilitating the access of power wheelchairs.
Table 1-3. International Patent Classification of the
personal conveyances specially adapted for patients or disabled persons, e.g.
personal conveyances specially adapted for patients or disabled persons, e.g.
wheelchairs / Motor-driven
personal conveyances specially adapted for patients or disabled persons, e.g.
wheelchairs / Parts, details or accessories
aspects of vehicles; Vehicles with special provisions for transporting
patients or disabled persons, or their personal conveyances, e.g. for facilitating access of, or for loading,
ramps, lifts or the like
Table 1-3 is the
top five citations of power
wheelchair patents. The citation number can represent the relative importance
of the patent. In this list, U.S. Patent 5,435,404 describes
a suspension mechanism to enhance the stability and to reduce the size of the power
wheelchair, as shown in Figure 1-6. U.S. Patent 5,575,348 also describes a power
wheelchair suspension system which was no anti-tip caster wheels. The adjustable
center of gravity mechanism also provided the user an adjustable seat and
seatback. U.S. Patent 4,634,941 describes a power wheelchair control method
which is pertained to feedback speed control. U.S. Patent 4,634,941 describes a
six-wheel power wheelchair chassis to increase the maneuverability.
Table 1-3. Citations
of power wheelchair patents
Powered mobility chair for individual
Electric wheelchair with improved control circuit
Powered wheelchair with adjustable center of
gravity and independent suspension
Figure 1-6. A suspension mechanism
In addition to
develop suspensions, control methods, and chassis of wheelchair, Staodyn, Inc.
designes a power-assisted wheelchair to help the user propel the wheelchair
himself / herself. The power-assist is provided by an electrical power unit
that includes a motor for driving each main wheel of the manual wheelchair, as
shown in Figure 1-7. The electrical power unit is removable so that the user
can remove the unit and fold the manual wheelchair. Following this new design concept,
Yamaha develops some power-assisted wheelchair by using a light and small
motor, recently. Figure 1-8 is the Yamaha’s product of power-assisted
Figure 1-7. Power-assist wheelchair and electrical
Figure 1-8. Power-assist
1.4 Robotic wheelchair
Miller and Slack
 first used the term “robotic wheelchair”. 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. Simpson  reviewed many recent studies
on the development of “smart wheelchairs” that can perform some autonomous
behaviors for mobility assistance, such as obstacle avoidance and navigation.
navigation is one of the major research issues in robotic wheelchair, since
mobility assistance is the fundamental function of a wheelchair. Prassler et
al.  developed robotic wheelchair MAid (Mobility Aid for Elderly and
Disabled People), as shown in Figure 1-9, to support and transport users with
limited motor skills. The system provides functions ranging from fully
autonomous navigation in an unknown crowded environment such as a railway
station to partially autonomous local maneuvers such as passing through narrow
doorways. Cruz et al.  proposed a landmark based navigation system and an
obstacle avoidance strategy for robotic wheelchairs. In their system, every
landmark was composed of a segment of metallic path and a RFID tag. All
landmarks were detected by inductive sensors and identified by a RFID reader.
Figure 1-9. Robotic wheelchair MAid
control scheme, which addresses how a human and a robot collaborate to perform tasks and to achieve goals [Fong
et al., 1999], is another important issue of the research in robotic wheelchairs
[Katsura and Ohnishi, 2004; Galindo
et al., 2006a; Holzapfel, 2008; Urdiales et al., 2011; 2010; Braga et al., 2011].
There is no supervisor in the collaborative control scheme, the user and the robotic
wheelchair exchange information and resolve differences together. The robotic
wheelchair is more like a partner to help the user find good solutions when
there are problems [Fong, 1999]. Galindo et al. [2006b] developed a robotic
wheelchair SENA to facilitate mobility of the disable people and older adults.
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.
1.5 Purpose of this research
presents the development of the “intelligent Robotic Wheelchair” (iRW), which intends to redefine the
wheelchair as the center of mobility, daily living, and healthcare of older
adults. Figure 1-10 illustrates the overall design concept of the iRW. The core of the iRW is a collaborative control designed
specifically for older adults’ declining abilities in perception, motor control,
and cognition. Technically, the iRW
is composed of an omni-directional vehicle, a multiple degree-of-freedom (DOF)
seat adjustment mechanism, and an information/communication module. The iRW is intended to enhance the usability
of wheelchair to increase the independent living and social participation for
the older adult, and therefore improve their quality of life.
Figure 1-10. Design
concept of the iRW
Figure 1-11 is
the current prototype of the iRW. The omni-directional
vehicle of the iRW uses four Mecanum
wheels to facilitate movement in all directions, including moving sideways, and
with zero radius of rotation. The iRW
requires much less space than do
general electric wheelchairs in turning and sideway maneuvers. Based on this omni-directional
vehicle, mobility assistance functions are design for three different
operators: the wheelchair user, caregivers, and the iRW itself performing autonomous behaviors. Five operation modes,
all mutually exclusive, are developed: obstacle
avoidance, joystick mode, handlebar mode, teleoperation, and indoor navigation.
Man-machine collaborative control is reflected in the assignment of
priorities to the three operators.
The multiple-DOF seat
adjustment mechanism is intended to increase the independence of the wheelchair
user, while maintaining a concise structure, light weight, and intuitive
control interface. This four-axis Stewart platform is capable of the motions of
heaving, pitching, and swaying to provide seat elevation, tilt-in-space, and
sideways movement functions. The geometry and types of joints of this mechanism
are carefully arranged so that only one actuator needs to be controlled,
enabling the wheelchair user to adjust the seat by simply pressing a button.
The seat is also equipped with soft pressure-sensing units to provide pressure
management by adjusting the seat mechanism once continuous and concentrated
pressure is detected.
information/communication module is in the form of an App running on a tablet
mounted on the armrest of the iRW.
Connected to blood pressure and blood glucose meters, the tablet serves as the
platform for tele-healthcare management. Through caring messages, timely
reminders, and photos sent by remote family members and caregivers, the tablet
is also the communication channel for the wheelchair user [Chen at al., 2011]. This
thesis focuses on the technical development and user evaluation of the mobility assistance functions and the
multiple-DOF seat adjustment mechanism of the iRW.
Figure 1-11. Current prototype of the iRW
The thesis is
organized as follows. Chapter 2 describes the mobility assistance design
of the iRW. Chapter 3 presents the technological
details of the indoor navigation function of mobility assistance design. The seat adjustment design based on the Stewart platform is then introduced
in Chapter 4. Chapter 5 describes the usability assessment of the iRW. Finally , Chapter 6 concludes this
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