Effect of Waveform in Haptic Perception of Electrovibration on Touchscreens
The perceived intensity of electrovibration can be altered by modulating the amplitude, frequency, and waveform of the input voltage signal applied to the conductive layer of a touchscreen. Even though the effect of the first two has been already investigated for sinusoidal signals, we are not aware of any detailed study investigating the effect of the waveform on our haptic perception in the domain of electrovibration. This paper investigates how input voltage waveform affects our haptic perception of electrovibration on touchscreens. We conducted absolute detection experiments using square wave and sinusoidal input signals at seven fundamental frequencies (15, 30, 60, 120, 240, 480 and 1920 Hz). Experimental results depicted the well-known U-shaped tactile sensitivity across frequencies. However, the sensory thresholds were lower for the square wave than the sinusoidal wave at fundamental frequencies less than 60 Hz while they were similar at higher frequencies. Using an equivalent circuit model of a finger-touchscreen system, we show that the sensation difference between the waveforms at low fundamental frequencies can be explained by frequency-dependent electrical properties of human skin and the differential sensitivity of mechanoreceptor channels to individual frequency components in the electrostatic force. As a matter of fact, when the electrostatic force waveforms are analyzed in the frequency domain based on human vibrotactile sensitivity data from the literature , the electrovibration stimuli caused by square-wave input signals at all the tested frequencies in this study are found to be detected by the Pacinian psychophysical channel.
KeywordsWaveform Electrovibration Perception Electrostatic forces Square Sinusoidal waves
The Scientific and Technological Research Council of Turkey (TUBITAK) supported this work under Student Fellowship Program BIDEB-2211. Also, Y.V would like to first thank Prof. Dr. Ozgur Birer for his valuable comments during discussions. Moreover, Y.V would like to acknowledge Ozan Caldiran, Gokhan Serhat, Amir Reza Aghakhani, Omer Sirin, and Utku Boz for their valuable comments and technical help during this study. Moreover, Y.V would like to acknowledge the initial help and support given by Ezgi Emgin and Enes Selman Ege. They introduced electrovibration to Y.V. and provided a quick start for her study. Also, Y.V would like to thank all subjects who participated in the experiments.
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