A heuristic-based approach to optimize keyboard design for single-finger keying applications

With the popularity of mobile devices, designing a keyboard for users who can only operate with a pointer or the eyes is a challenging task. In this paper we present a methodology and keyboard designs that attempt to optimize the key arrangement so that movement time, as defined by Fitts' law, is minimized. Numerical simulations show that the present day keyboards and arrangements are not optimal for such applications. Three keyboard shapes, which included an existing design and two others were selected based on symmetry and compactness and were compared with two soft keyboards, FITALY and Metropolis. An integer programming model was formulated considering the character transition frequency of words in the English language. The problem was solved using a simulated annealing heuristic. One of the proposed designs called "YLAROF" with a rectangular design and a symmetric layout with characters laid in an "I" shape showed stable and consistent performance, when tested with 20 test cases. Relevance to industry: When holding a mobile device, only one hand or one pointer is available for data input. Thus, it is important to minimize movement time in order to improve performance and minimize potential fatigue. The methodology presented and the proposed keyboard designs can be used and configured in existing products quite easily.