1 Introduction

Taiwan is the one of most important countries that manufactures electronic wheelchairs. The major sales of the wheelchairs are through exports to the European Union and USA. For most users facing difficulty in travel, it is one of the common ways of assistance through the mobility assistive technology (Souza et al. 2010). Therefore, more time must be invested in the development and design of electronic wheelchairs and the future of intelligent auxiliary system. However, when users operate the electronic wheelchair, they should be able to accurately sense the surrounding environment and predict possible obstacles or hazards. For most users, electronic wheelchair control is still difficult. The manufacturing process for an electronic wheelchair would include (1) seat and posture transformation mechanism system; (2) drive system: drive motor, reducer (gear group), electromagnetic brake, clutch, anti-tilting wheel, etc.; (3) electronic control system: control mode, input mode, controller, monitor, and power supply; (4) human-computer interface: input device and output device. The key aspect in operating an electronic wheel chair are accessibility and maneuverability. According to the World Health Survey in 2015, approximately 785 million people are suffering from disability and living inconvenience globally (Mortenson et al. 2015). National Institute on Aging, NIA (2010) points out that more than 38% of the people with difficulty in walking are over 65 years of age. From 2000 to 2010, approximately 3.1% of disabled people changed their traditional wheelchairs to electronic wheelchairs (Loraine et al. 2010). There are approximately 2 million new wheelchair users every year. The traditional wheelchair industry revenue grew at an average annual rate of 2.5% from 2009 to 2014. Approximately 1.825 million wheelchair users are of the age of 65 or are older. Particularly, 11.2% of adult wheelchair users are graduates, compared to the 21.6% of the general adult population (Reznik 2015).

Karma Co. Ltd. is the one of the most important companies that manufactures electronic wheelchairs in Taiwan. Karma’s product occupation in the market of Spain was 50%, Japan was 20%, Taiwan was 80%, Singapore was 60%, and Thailand was 80% in 2016. Karma’s KP-25.2 electronic wheelchair was suitable for both indoor and outdoor use in Taiwan. Figures 1 and 2 show the appearance, user interface, and size of an electronic wheelchair. As the research report of Transparency Market Research (TMR) shows that the Global electronic wheelchair market was valued at USD 1.23 billion in 2013, growing at an estimated CAGR of 19.2% over the forecast period from 2014 to 2020. Electronic wheelchairs are the battery supported wheelchairs which reduce the user’s dependence on any external human assistance for movement (TMR 2017).

Fig. 1.
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Karma KP-25.2 electronic wheelchair (on the right side is the user interface of the electronic wheelchair)

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Fig. 2.
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KP-25.2 electronic wheelchair

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In 1993, Nielsen defined the concept of ‘Usability Engineer’ (Nielsen and Kaufmann 1993; del Galdo and Nielsen 1996). Nielsen stated that usability is a measurement of the quality that the user experiences when interacting with a system. He also states that good usability is composed of learnability, low error rate, memorability, efficiency, and satisfaction (Preece et al. 1994). To understand the experience of a user operating an electronic wheelchair, the usability evaluation for the user interface of an electronic wheelchair is presented in this study.

2 Research Method

The study was conducted in two stages. First, the questionnaire survey was set for the interface design of the electronic wheelchair; second, participants operating the electronic wheelchair were observed.

2.1 Image Stimuli

Table 1 shows the 49 icons used in the questionnaire survey. The following six group icons were included: power icons, alarm icons, direction icons, speed adjustment icons, battery status icons, and stop icons. All the icons were monochromatic shapes. A total of 27 participants assessed these 49 icons on a scale of 10 (‘1’ indicated a poor icon; ‘10’ indicated the best icon) on the questionnaire.

Table 1. The 49 icons used in the questionnaire survey.
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2.2 Observation

In the second stage, 20 undergraduates from Department of Creative Product Design and Management at Far East University in Taiwan were selected on the basis of convenience sampling. Those with less than perfect vision used glasses or contact lenses to correct their vision; hence, all subjects were able to see normally. All of them had no experience in operating the electronic wheelchair. The procedure of operation included task introduction, operation of electronic wheelchair, and questionnaire survey (subjective satisfaction). The experiment for observing participants’ operation experience of the electronic wheelchair was divided into ten steps (see Fig. 3). One-way ANOVA was used to analyze the operation time between the male and female participants by using SPSS software. Figure 3 shows the procedure of the task.

Fig. 3.
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Procedure of the task

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3 Data Analysis and Results

3.1 Subjective Assessment Analysis

Data analysis was done according to the participants’ subjective assessment of the icon cognitive. The analysis of mean and standard deviation (SD) results demonstrated that the new icons are better than present icons. The power icon, alarm icon, speed adjustment icon, and the battery icon showed that the new icons are better than the present icons. Norman (1988) pointed out that a good interface (or feedback) provides good user experience (Shackel 1990). These subjective assessment results suggest that new icons will lead to a correspondingly better experience. The power icon, alarm icon, speed adjustment icon, and battery icon received relatively high scores from the participants. Since the present electronic wheelchair had no stop function, the direction-control was based on the control lever. Conversely, when the participants performed the stop icon and direction icon assessment tasks, the participants gave icon 6 a score of 4 and icon 4 a score of 7. (see Table 2).

Table 2. Results of icon assessment
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3.2 Results of Analysis

Generally, when participants used the electronic wheelchair, they could easily navigate forward and backward, as well as turn right and left by using the control lever (see Fig. 4). The results showed that there was no significant variation between the usage by male and female participants (F (1, 198) = .065, p > .05). The correlation analysis performed between the tasks revealed that the operation of power and of speed adjustment exhibited significant direct correlation (r = .63, p < .001). The left/right and forward/backward operations exhibited a significant direct correlation (r = .97, p < .001).

Fig. 4.
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Operation of electronic wheelchair

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3.3 Suggestion for Icons Design

The new icons were selected from the icons that received a higher score in the questionnaire. As shown in Table 2, this study developed the user interface of the electronic wheelchair, as shown in Fig. 5. The right side of Fig. 5 shows the new icons of the user interface; the icons from top to bottom are the power switch, alarm, speed adjustment, and the battery icon. The speed adjustment should replace the layout from left/right to top/bottom. The upper part of the speed adjustment icon is for increasing the speed, and the lower part is for decreasing the speed. The battery icon should be integrated into LED’s backlight to indicate battery life to help the user understand the battery status at night.

Fig. 5.
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Simulated icon for user interface of electronic wheelchair

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4 Discussion

Norman (1988) observed that the mental model included the user’s model, design model, and system image. He had advocated that the user interface should be based on user-centered design. In this study, we found that the user interface, which included the power icon, alarm icon, speed adjustment icon, and the battery icon, should be redesigned to provide good user experience. This study suggests a new power icon, alarm icon, speed adjustment icon, and battery icon. The 7 Principles of Universal Design guide the design of environments, products, and communications. The following 7 principles were included: 1. equitable use; 2. flexibility in use; 3. simple and intuitive use; 4. perceptible information; 5. tolerance for error; 6. low physical effort; 7. size and space for approach and use. In the second stage, we found that the electronic wheelchair could be operated easily. It was observed that the electronic wheelchair is very simple and intuitive in terms of direction operation for a novel user. KP-25.2 is in accordance with items 1, 2, 3, and 6 of the 7 Principles of Universal Design.