A User Centric Model to Design Tactile Codes with Shapes and Waveforms
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abstract
The tactile medium of communication with users is appropriate for displaying information in situations where auditory and visual mediums are saturated. There are situations where a subject's ability to receive information through either of these channels is severely restricted by the environment they are in or through any physical impairments that the subject may have. Usually, the tactile information is displayed in the form of codes. These tactile codes can vary in both shape, and waveform of the code. Designers use variations shape or waveform as tactile codes. Usability of tactile codes depends on the users' ability to distinguish between these variations. We have built two vibrotactile displays, Tactor I and Tactor II, each with nine actuators arranged in a three-by-three matrix with differing contact areas that can represent a total of 511 shapes. We used two dimensions of tactile medium, shapes and waveforms, to represent verb phrases and evaluated ability of users to perceive the tactile code. We propose a measure to rate the distinguishability between two shapes, a graph model with shapes as nodes and distinguishability between shapes as weights of edges, and an algorithm to cluster distinguishable shapes. We evaluated the distinguishability of shapes from the clustering algorithm against the experimenter's choice of shapes for tactile codes with eight users. The results show that the users can distinguish the shapes proposed by the clustering algorithm with higher accuracy than the shapes chosen by the experimenter. The results from the study also show that users can identify simultaneously presented waveforms and shapes in the codes without reduction in waveform identification accuracy. 2014 IEEE.
