Design of a Tactile Instrument to Measure Human Roughness Perception in a Virtual Environment

This paper presents the experimental results on the measurement of human texture perception in virtual environments. The experiment is conducted with a haptic tactile instrument that provides sensations of rough textures directly to the fingertip of the users. It consists of a brush and a DC motor. The brush rubs directly against the user´s fingertip. Simulated texture is felt through an aperture on the tactile actuator where the users place their fingertip. The speed and direction of the brush are varied to control the roughness of the virtual surface and to determine the effect of either variable on perceived roughness. The actuator is designed to be attached to an existing force feedback device in order to create an interface that can provide force feedback and tactile feedback. The magnitudes of rough textures are measured through this device by comparing the virtual textures with real sandpapers of different grit sizes. Through human factor testing, it is found that the direction of rotation has negligible effects on roughness perception when the time gap between two consecutive stimuli is as large as 10 s. However, when the time gap is reduced to 0.5 s, the effects of direction become prominent. The just noticeable difference with respect to speed is found to decrease as the base speed of the brush increases. The results also show that although each subject´s perception of roughness is biased using various sandpapers, the measured data is divided between two trends. One group of users perceives the roughness to increase with increasing speed, while the other group perceives the roughness to decrease.