Effect of update rate on perceived instability of virtual haptic texture

This study investigates the effect of update rate on the perceived quality of haptic virtual textures, focusing on one type of perceived instability called "buzzing." Buzzing refers to the high-frequency noises that may emanate from a force-feedback device during haptic texture rendering. We first present a simulation of a haptic texture rendering system that explicitly models the sampled-data nature of the system. The simulation shows that a slow haptic update rate can significantly increase the high-frequency noise in the reconstructed force command sent to the haptic interface. This noise may excite the structural resonance of the haptic interface and result in a high-frequency buzzing at the interaction tool that a user holds. A subsequent psychophysical experiment, conducted over a wide range of update rate (250 Hz - 40 kHz), has confirmed the simulation results. The results show a 278% increase in the maximum stiffness (0.325 - 0.904 N/mm over the update rates tested) that could be used for rendering perceptually "clean" virtual haptic textures. These results argue for haptic update rates that are much higher than the widely-accepted value of 1 kHz. Considering that an application requiring hard surface rendering needs a stiffness value of at least 0.8 - 1.0 N/mm, we recommend a haptic update rate in the range 5-10 kHz for perceptually stable haptic texture rendering.