Experiments in Surface Perception using a Fingertip Haptic Display

Experiments in Surface Perception using a Fingertip Haptic Display by Steven Craig Venema Chairperson of Supervisory Committee: Professor Blake Hannaford Department of Electrical Engineering A haptic display provides the mechanical analog of a physical environment for our sense of touch in a virtual reality (VR) simulation system. In this dissertation, we explore the design and implementation of a planar fingertip haptic display (FHD) mechanism. We first present a new technique for analysing the reachable workspace of mechanisms that have stochastic kinematic parameters. This technique is used to develop a stochastic representation of the reachable workspace of the human finger. Using this finger workspace, we present a method for selecting the kinematic parameters of a five-bar linkage mechanism to match the finger workspace while providing high-quality force output capability over the entire mechanism workspace. We then use this haptic display in psychophysical experiments which explore the human perception of geometric surface discontinuities on a haptically rendered virtual surface. Specifically, the experiments examine how the ability to perceive and locate both first-order and second-order surface discontinuities is affected by both the magnitude of the discontinuity and by the particular set of control gains used in haptically rendering the discontinuity. The results of these experiments are relevant to haptic simulation systems which approximate complex curved surfaces with planar facets: the intersection between facets is a form of surface discontinuity and the perceived smoothness of the surface is likely related to the magnitude of the change in surface gradient at these intersections.