Study on effects of surface properties in haptic perception of virtual curvature

Stiffness and friction are regarded as important haptic cues for designers of haptic virtual environments. One virtual concave curvature discrimination test based on randomised block design with three factors, radius, stiffness and friction, has been designed and performed to understand human perceptual performance. Randomised block design with three factors can separately distinguish the subject random effect from main effects. In the experiment, subjects compare two virtual sequential concave surfaces and identify the surface having the higher curvature. The statistical results based on Analysis of Variance (ANOVA), regression tree and logistic regression indicate that variations in curvature discrimination may be slightly attributable to varying virtual haptic stiffness between 0.3 N/mm and 0.7 N/mm. Also, a clear interaction in radius and friction coefficient between 0 and 0.2 is found. While the experimental results are limited by some factors, the authors believe that the resulting effects of haptic surface properties may serve to improve the fidelity of medical virtual reality simulators.