Six principal modes of vibrotactile display via stylus

Abstract

Vibrotactile display can significantly enhance the haptic fidelity of tool-mediated interaction with virtual surfaces. Although there has been significant research on this topic, there is little known about vibrotactile perception when using torque-based actuation, nor how it is perceived in comparison to force-based actuation. This study characterizes the vibrotactile detection thresholds in the frequency range of 20-250 Hz of ten human subjects holding a stylus with a precision grasp. For the first time, we consider all six principal modes of vibrotactile display rendered at the haptic interaction point of the stylus, which includes three orthogonal force directions and three orthogonal torque directions. We find that subjects are far more sensitive to torque signals about the shaft of the stylus than to torque signals orthogonal to the shaft. We find that, at low frequencies, subjects are less sensitive to force signals parallel to the shaft of the stylus than to force signals orthogonal to the shaft. We find that the thresholds for force and torque signals applied orthogonal to the shaft of the stylus can be approximately equated by considering the reaction moment felt at the grasp point, which enables all six principal modes to be quantitatively compared.