Psychophysical study of air jet based tactile stimulation

Haptic rendering technologies are becoming a strategic component of the new Human-Machines Interfaces. Many existing devices generally operate with intrusive mechanical structures that limit rendering and transparency of the haptic interaction. In the context of the design of a novel non-contact haptic device that exploit the air jet tactile stimulation with long distance, we carried out psychophysical experiments in order to characterize the human perception of the air jet tactile stimulation. This study focuses on the stimulation of the user´s hand palm. Fluid mechanics suggests that perceived parameters of the air jet stimulation can be controlled by the air jet flow rate, the nozzle geometry, and the distance between the nozzle and the hand palm. In this paper we investigate how these control variables affect the perceived force on the hand palm. Two psychophysical studies were carried out. The first experiment investigated three distances from the air nozzle to determine the absolute threshold of the air flow rate on the hand palm. Results reveal that there is a linear relationship between the perceived absolute threshold and the distance from the hand palm to the nozzle. The second psychophysical experiment was made to determinate the just noticeable difference of the air flow rate according to three referential stimuli. Then we estimated the Weber fraction. These two results are important for the display control and will be used further for the design of the future noncontact haptic device.