Developing Rich Haptic Key-Click Feedback
Three studies were conducted in an attempt to develop distinctive haptic key-click feedback. Study 1 investigated the perceptual dimensions associated with manual key clicks, with the goal of developing realistic haptic key-click feedback signals for virtual keys. We first harvested eight adjective pairs for describing the haptic feel of button and key presses from native English speakers. We then conducted a multidimensional scaling (MDS) experiment where participants provided adjective ratings and grouping data for twenty-three buttons and keys. An MDS analysis of the grouping data led to either a two-dimensional (2-D) or three-dimensional (3-D) solution. By projecting adjective ratings onto the MDS solution spaces, we found the 2-D perceptual space to be an adequate representation of human perception of manual key clicks. The two perceptual dimensions are determined to be shallow-deep and rough-smooth. Study 2 correlated the physical parameters measured from manual key clicks to the two perceptual dimensions of shallow-deep and rough-smooth. We projected all 23 keys in the MDS space onto the perceptual dimensions and obtained a perceptual score for each key on each perceptual dimension. We then generated a database of force and acceleration measurement profiles recorded from key clicks. After correlating the parameters extracted from these profiles and the two perceptual dimensions, we found that actuation force of key clicks and the duration of a key click acceleration profile correlate to the shallow-deep dimension, with large force and short duration contributing to the perception of deep. For the rough-smooth dimension, high peak acceleration attributed to the perceptual of rough. Study 3 used findings from Studies 1 and 2 as the guidelines for designing virtual key click signals varying in peak acceleration and duration. A cellphone mockup prototype was provided by the project sponsor that showcases the various key click sensations achievable by pressing a virtual Home button. We examined the distinctiveness of our designed signals by conducting an absolute identification (AI) experiment where participants were asked to identify 3 intensity levels and 3 duration levels. For the 3 participants involved in our pilot study, we estimated the channel capacity to be approximate 3 items for our designed signals.
Tan, Purdue University.
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