Design and Testing of a Fingertip Haptic Interface

Abstract

Fingertip force sensitivity threshold, human resolution, multimodal feedback, and interface miniaturization for ultra-mobile devices such as smart watches and glasses are investigated in this thesis. An FHI (Fingertip Haptic Interface) was designed and built to measure the position and force resolution of the human fingertip. The thumb and forefinger resolutions were identified as 212um and 133um, respectively. The force threshold at which the forefinger detects pulses was found experimentally to be F(t) = .148t + 28.7 where t is the pulse width in ms, and F(t) is the fingertip force in mN. It was found that visual feedback dominates user input tasks, but during eyes-free usage haptic feedback provides an improvement that quickly dissipates with increased task difficulty. Finally, the smallest target size that can be reliably selected was found to be two to three times the smallest resolution of the index finger or thumb.