A method for controlling tactile sensation of surface roughness using ultrasonic vibration

A method is proposed for controlling the tactile sensation of surface roughness. This method creates a smoother feeling on a surface by applying ultrasonic vibration, with a few micrometers amplitude, to the surface. The sensation can thus be controlled without altering the actual surface profile. Experiments using five to ten subjects showed the properties of the proposed method, such as the effect of ultrasonic vibration on tactile sensation, the positive relationship between the generation of a smooth feeling and vibration amplitude, and the dependence on vibration frequency. The typical perceived feeling with this method, `air smoothness´, is postulated to be due to the `squeeze air film effect´ between the finger and the surface. The calculated squeeze force qualitatively agreed well with our experimental results. The proposed method also enables the generation of resistant impressions, such as `the surface is rougher/more sticky´ and `a virtual protrusion exists on the surface´, when the duration of the ultrasonic vibration is short enough