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

IntroductionJapan'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 ％）

20052010

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

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