Interfaces

A first interface is the smartphone application that works as a universal remote controller. This application automatically discovers the surrounding BTSwitch modules and displays the discovered appliances. Within the application, the user can configure each plug and power strip with custom names and images. The display and configuration interfaces for the Android platform are illustrated in Figure 4.25. As shown in the screenshot on the right in Figure 4.25, the graphical interface can be customized according to user preference with a particular focus on size and position of the buttons. On the main interface of the application (Figure 4.25, left), each button has different colors to indicate its state; the green color indicates that the plug is on; the red color indicates that the plug is off and the orange color indicates the transition while the message is being processed. Note that in normal conditions, the time to process a message is less than two hundred milliseconds. To control an appliance, the user simply selects the desired BTSwitch power strip; then, the corresponding appliances are shown in the interface. The desired appliance is turned on or off in real-time by tapping on the corresponding button.

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Figure 4.25 The interfaces of the smartphone application: on the left, the main interface to interact with the ap- pliances; in the center the interface to configure a particular power strip; on the right, the interface application

configuration.

Along with the interaction performed through the smartphone, the natural interface based on the functional gesture using the pointing gesture as presented in the previous section has been implemented. The only difference with the approach of the previous test is the number of tracked joints: in order to optimize the user tracking for people in a sitting position (i.e., people on a wheel-chair), the joints of the legs were filtered. The spatial model for the context information and the gesture detection was reconstructed also in a 3D graphical representation as depicted in Figure 4.26. The 3D axes represent the user’s arm with the yellow extension for the calculation of the target object. In this case, the smart objects were modeled as cubes.

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Figure 4.26 The 3D graphical representation of the pointing gesture recognition; the red line is the ray and the cubes are the smart objects. 4.4.1.3 Usability Test

The scenario was set up in an office context as shown in Figure 4.27. The user is the first person entering in his/her work office; therefore, he/she has to turn the light on, to power on his/her personal computer and to start working. After a while, the office temperature raises and the user decides to turn the fan on for some freshness. He/she continues working for some time, then, before leaving his/her office, he/she turns all the electrical appliances off.

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Figure 4.27 Test scenario.

The system was tested with 13 users (1 person with reduced mobility on his own wheelchair and 12 able-bodied subjects on an electric wheelchair) with age ranging from 21 to 34. The experiment was composed of two phases; one phase involved the user following the office scenario controlling the electrical appliances through the smartphone paradigm. The other phase consisted in accomplishing the same scenario controlling the electrical appliances through the natural interaction paradigm. The order of the two phases was randomly chosen for each subject. After each phase the subject had to fill in the SUS questionnaire (Brooke, 1996). At the end of the whole experiment the subject filled in a questionnaire with five open questions: which interaction paradigm he/she preferred and the advantages and the disadvantages of each interaction paradigm.

The users’ evaluations assessed the smartphone interaction paradigm usability as excellent with an average SUS score of 91.3 points and a standard deviation of 7.5 points. The system with the natural interaction paradigm usability obtained an average SUS score of 84.2 with a standard deviation of 7.6.

According to users’ feedback written in the questionnaires, the main advantages of the smartphone interaction paradigm are that it is reliable, intuitive, requires minimal effort, and that all the controllable appliances are visible on the screen

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with direct visual feedback of their state. The main disadvantages have been identified as the required precision to press a button on the touch screen and the need of carrying a handheld device. The main advantages of the natural interaction paradigm are that it is very intuitive, provides a natural interaction mechanism (absence of handheld device) and a direct visual feedback from the physical appliances. The main disadvantages are the need to move the wheelchair to control specific appliances, and the potential fatigue caused by the deictic gestures.

The subject with impaired mobility preferred the smartphone interaction paradigm. He specially emphasized the fact that most electric wheelchair users already have a smartphone attached to their wheelchair and the convenience of such a system for people with reduced mobility of the upper limbs. On the other hand, he also identified the advantage of the natural interaction paradigm for people with reduced mobility of the fingers that could find the smartphone interaction more troublesome. He also stated that, for both cases, a vocal modality could be a great additional feature.