Forcetap: extending the input vocabulary of mobile touch screens by adding tap gestures

Abstract

We introduce an interaction technique that increases the touch screen input vocabulary by distinguishing a strong tap from a gentle tap without the use of additional hardware. We have designed and validated an algorithm that detects different types of screen touches by combining data from the built-in accelerometer with position data from the touch screen. The proposed technique allows a touch screen input to contain not only the position of a finger contact, but also its type, i.e., whether the contact is a 'Tap' or a 'ForceTap.' To verify the feasibility of the proposed technique we have implemented our detection algorithm in experiments that test cases of single-handed, two-handed, immersive, and on the move usage. Based on the experimental results, we investigate the advantages of using two types of touch inputs and discuss emerging issues. Finally, we suggest a design guideline for applying the proposed technique to touch screen applications, and present possible application scenarios.