Aliveness: perceived instability from a passive haptic texture rendering system

This paper reports new findings of our ongoing research on perceived instability that human users frequently experience from interacting with virtual textures rendered with a force-feedback haptic interface. Our work is aimed at a better understanding of a new type of perceived instability called "aliveness", which was discovered during our previous psychophysical experiments performed using a popular texture rendering method (spring model with fixed force directions) and a common texture model (position-based sinusoidal grating). We first examine the perceptual and physical characteristics of the proximal stimuli that cause the perception of aliveness in virtual textures. It leads to the hypothesis that the virtual environment model used for computing texture-perturbing forces, not the traditional control-related instabilities of the haptic texture rendering system, is responsible for aliveness perception. We show that this conjecture is true by applying passivity-based stability theory to the position and force data measured during user interaction with virtual textures. Examples of the data where the haptic texture rendering system is passive (therefore stable) and aliveness is perceived are provided to substantiate our conclusions. Our results point to the importance of designing haptic texture rendering methods and models that are free of perceptual artifacts.