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Liu, Yuanting (2012): Multimodal interaction: developing an interaction concept for a touchscreen incorporating tactile feedback. Dissertation, LMU München: Faculty of Mathematics, Computer Science and Statistics
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Abstract

The touchscreen, as an alternative user interface for applications that normally require mice and keyboards, has become more and more commonplace, showing up on mobile devices, on vending machines, on ATMs and in the control panels of machines in industry, where conventional input devices cannot provide intuitive, rapid and accurate user interaction with the content of the display. The exponential growth in processing power on the PC, together with advances in understanding human communication channels, has had a significant effect on the design of usable, human-factored interfaces on touchscreens, and on the number and complexity of applications available on touchscreens. Although computer-driven touchscreen interfaces provide programmable and dynamic displays, the absence of the expected tactile cues on the hard and static surfaces of conventional touchscreens is challenging interface design and touchscreen usability, in particular for distracting, low-visibility environments. Current technology allows the human tactile modality to be used in touchscreens. While the visual channel converts graphics and text unidirectionally from the computer to the end user, tactile communication features a bidirectional information flow to and from the user as the user perceives and acts on the environment and the system responds to changing contextual information. Tactile sensations such as detents and pulses provide users with cues that make selecting and controlling a more intuitive process. Tactile features can compensate for deficiencies in some of the human senses, especially in tasks which carry a heavy visual or auditory burden. In this study, an interaction concept for tactile touchscreens is developed with a view to employing the key characteristics of the human sense of touch effectively and efficiently, especially in distracting environments where vision is impaired and hearing is overloaded. As a first step toward improving the usability of touchscreens through the integration of tactile effects, different mechanical solutions for producing motion in tactile touchscreens are investigated, to provide a basis for selecting suitable vibration directions when designing tactile displays. Building on these results, design know-how regarding tactile feedback patterns is further developed to enable dynamic simulation of UI controls, in order to give users a sense of perceiving real controls on a highly natural touch interface. To study the value of adding tactile properties to touchscreens, haptically enhanced UI controls are then further investigated with the aim of mapping haptic signals to different usage scenarios to perform primary and secondary tasks with touchscreens. The findings of the study are intended for consideration and discussion as a guide to further development of tactile stimuli, haptically enhanced user interfaces and touchscreen applications.