Frequency modulation effect on the vibrotactile perception

Abstract

The tactile sensation from the receptors has five basic properties available to obtain information from a vibrotactile stimulus: intensity, frequency, waveform, duration and location. Especially, intensity and frequency are fundamental stimulation elements in the case of tactile feedback on the skin. To understand the effect of intensity, there have been many relevant psychophysical studies such as stimulus detection thresholds and sensation level of somatic sensation at each frequency. Many devices generate tactile feedback with the intensity modulation. However, tactile feedback with frequency modulation is not common in many devices. This dissertation tries to investigate the frequency modulation effect on vibrotactile perception. Chapter 2 presents methods to feel the tactile stimuli with frequency modulation As a preliminary test, the vibrotactile threshold of the right index finger was measured at the frequency band of 6.31Hz to 398.1Hz and three small contactor areas $(0.20mm^2, 0.79mm^2, and 3.14mm^2)$. The experimental curve was shown as a U-shape with a minimum around the frequency of 250Hz. A transition of the sensation level after frequency modulation was noted under the same amplitude (Chapter 2.1). Based on this finding, alternation of spatial patterns is investigated by modulating the temporal pattern. It is attempted to observe what effects with the frequency modulation of vibration elements produce in representing a tactile shape. The tactile shapes were modulated based on frequency difference at a constant amplitude through a tactile feedback array of 30 (5×6) pins that simulated the finger pad. Experimental results show that participants can sense height modulation during modulating frequency and can discriminate the three basic tactile shape patterns, which were generated with different frequencies at a constant amplitude. These experiments proved that spatial information can be represented by modulating temporal information (chapter 2.2)....