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A study of intuitive electric
wheelchair control interface
based on weight shift
利用直覺性的重心轉移來控制電動輪椅的研究
Outline
Introduction
Materials and Methods
Results
References
Introduction
Japan's percentage of the population aged over 65 is almost
20%, according to estimates released report by the Japan
Ministry of Internal Affairs Bureau in 2005.
In addition, it will expect total population of over 25% reaches
over 65 years old.
Such a rapidly growing aging society in Japan, the role of
electric wheelchair becomes important personal vehicle to
enhance the mobility.
Because of difficulty of driving interface for electric
wheelchair, the number of accidents that related to electric
wheelchair operation is also increasing.
Introduction
男女別にみると、男性は1258万人
（男性人口の20.3％）、女性は1685
万人（女性人口の25.8％）
2005
2010
統計局ホームページ
Introduction
The conventional electric wheelchair
control interface can be classified into
two groups;
(1) Vehicle steering type interface
(2) Joystick type interface
Introduction
However to use joystick to control electric
wheelchair safely, several training is necessary.
If we can implement intuitive interface to control
electric wheelchair, driver can reduce training
process time.
There are two approaches to implementing the
intuitive interface. One is cognitive aspect
implementation and the other is safety aspect
implementation.
Materials and Methods
Electric wheelchair
Proposed intuitive control interface Fig.1 shows
proposed intuitive control interface for electric
wheelchair which is based on load cell to measure
weight shift on the wheelchair sheet. To measure
the weight shift on the wheelchair sheet, three load
cells are placed.
Signal processing
In order to control based on driver's
weight shift, we employ PSoC
(Programmable System on Chip) as
electric wheelchair driving controller.
Measurement of attitude
of driver
In order to detect attitude of electric wheelchair
driver, we use three load cells to measure
distribution of weight.
According to measurement of three different parts
of weight distribution shown in Fig.2, we can
calculate barycentric position can be described
Problem description
The problems considered here are
How to implement controller based on
intuitive driving
How to implement controller based on
safety aspect
Compare both designed controller based
on actual driving feeling
The construction of the controller
Controller design based
on cognitive aspect
1. if (barycentric position is forward) and
(barycentric movement speed is forward) then
(speed forward)
2. if (barycentric position is right) and (barycentric
movement speed is right) then (steering right)
3. if (barycentric position is back) and (barycentric
movement speed is back) then (speed back)
4. if (barycentric position is left) and (barycentric
movement speed is right) then (steering left)
Controller design based
on safety aspect
1. if (barycentric position is forward) and
(barycentric movement speed is forward) then
(speed back)
2. if (barycentric position is right) and (barycentric
movement speed is right) then (steering left)
3. if (barycentric position is back) and (barycentric
movement speed is back) then (speed foward)
4. if (barycentric position is left) and (barycentric
movement speed is left) then (steering right)
Experiments
To confirm the validity of
proposed method, we
conducted three types of
experiments for each two
aspect of designs with
the newly developed
interface.
(1) Straight line driving.
(2) Slalom-course driving.
(3) Position stopping.
Experiments
(1) Straight line driving
(2) Slalom-course driving
(3) Position stopping
Results
Table.1 shows the questionnaire result of the
experiments that used the design of cognitive
aspect.And by the questionnaires, result can be
summarized as following evaluations.
It is easy to imagine shifting the weight in the
direction of drive. It doesn’t take long to grasp the
technique of drive.
There are inertial effects, it is difficult to sit up for
brake and stop smoothly on the high-speed
running electric wheelchair.
Result of the questionnaire
Results
Table.2 shows the questionnaire result of the experiments
that used the design of safety aspect. And by the
questionnaires, we got the following evaluations.
Participants have a habit that turns their body to the direction
they wish to go. To get used to drive takes longer than the
design that implemented cognitive aspect.
In order to brake, they bend down and shift the weight
forward. When the electric wheelchair stops, they have few
unintentional speed changes by inertial effect.
Result of the questionnaire
References
http://www.stat.go.jp/index.htm
パンフレット統計局・政策統括官
（統計基準担当・統計研修所 （平成21年版）
Manabu SHIMIZU, Raise MORI, Kazuyuki KOBAYASHI,
Kajiro WATANABE, A study of a clothoidal path generation
for omni-directional camera based autonomous vehicle, ,
SICE annual Conference, Aug 2005, pp.3527-3530, (2005)
Nakajima Yasuhiro, Yasuda Seiki, Yoshinari Satoshi,
Watanuki Yukihiro, Tadano Shigeru, Development of a
touchpad controller for an electric wheelchair, Dynamics and
Design Conference 2001, p. 346
Thank you
for your attention