ForceBoard: Subtle Text Entry Leveraging Pressure

ForceBoard is a pressure-based input technique that enables text entry by subtle motion. To enter text, users apply pressure to control a multi-letter-wide sliding cursor on a one-dimensional keyboard with alphabetical ordering, and confirm the selection with a quick release. In particular, we examined the error model of pressure control for successive and error-tolerant input, which was then incorporated into a Bayesian algorithm to infer user input. Moreover, we employed tactile feedback to facilitate pressure control. The results showed that text entry rate achieved 4.2 WPM (Words Per Minute) for character-level input, and 11.0 WPM for word-level input after 10 minutes of training. Users subjectively reported ForceBoard was easy to learn and interesting to use. These results demonstrated the feasibility of applying pressure as the main channel for text entry, and that ForceBoard can be useful for subtle interaction or when interaction is constrained.  [Publication Available]