Roughness perception of virtual textures displayed by electrovibration on touch screens (original) (raw)
Related papers
The physical basis of perceived roughness in virtual sinusoidal textures
IEEE transactions on haptics
Using a high-fidelity haptic interface based on magnetic levitation, subjects explored virtual sinusoidal textures with a frictionless probe and reported the subjective magnitude of perceived roughness. A psychophysical function was obtained spanning 33 levels of spatial periods from 0.025 to 6.00 mm. Kinematic and dynamic variables were recorded at 1,000 Hz and used to derive a set of variables to correlate with the psychophysical outcome. These included position, velocity, kinetic energy, instantaneous force (based on acceleration), mean force, and variability of the z-axis force signal from the power spectral density. The analysis implicates power of the force signal as the physical correlate of perceived roughness of sinusoidal textures. The relationship between power and roughness held across the range of spatial periods examined.
Tactile Roughness Perception of Virtual Gratings by Electrovibration
IEEE Transactions on Haptics, 2019
Realistic display of tactile textures on touch screens is a big step forward for haptic technology to reach a wide range of consumers utilizing electronic devices on a daily basis. Since the texture topography cannot be rendered explicitly by electrovibration on touch screens, it is important to understand how we perceive the virtual textures displayed by friction modulation via electrovibration. We investigated the roughness perception of real gratings made of plexiglass and virtual gratings displayed by electrovibration through a touch screen for comparison. In particular, we conducted two psychophysical experiments with 10 participants to investigate the effect of spatial period and the normal force applied by finger on roughness perception of real and virtual gratings in macro size. We also recorded the contact forces acting on the participants' finger during the experiments. The results showed that the roughness perception of real and virtual gratings are different. We argue that this difference can be explained by the amount of fingerpad penetration into the gratings. For real gratings, penetration increased tangential forces acting on the finger, whereas for virtual ones where skin penetration is absent, tangential forces decreased with spatial period. Supporting our claim, we also found that increasing normal force increases the perceived roughness of real gratings while it causes an opposite effect for the virtual gratings. These results are consistent with the tangential force profiles recorded for both real and virtual gratings. In particular, the rate of change in tangential force (dFt/dt) as a function of spatial period and normal force followed trends similar to those obtained for the roughness estimates of real and virtual gratings, suggesting that it is a better indicator of the perceived roughness than the tangential force magnitude.
The perceived roughness of resistive virtual textures
ACM Transactions on Applied Perception, 2006
In previous work, we demonstrated that people reliably perceive variations in surface roughness when textured surfaces are explored with a rigid link between the surface and the skin [e.g., Klatzky and Lederman 1999; Klatzky et al. 2003]. Parallel experiments here investigated the potential of a force-feedback mouse to render surfaces varying in roughness. The stimuli were surfaces with alternating regions of high and low resistance to movement in the x (frontal) dimension (called ridges and grooves, respectively). Experiment 1 showed that magnitude ratings of roughness varied systematically with the spatial period of the resistance variation. Experiments 2 and 3 used a factorial design to disentangle the contributions of ridge and groove width. The stimuli constituted eight values of groove width at each of five levels of ridge width (Experiment 2) or the reverse (Experiment 3). Roughness magnitude increased with ridge width while remaining essentially invariant over groove width. ...
Effect of Waveform on Tactile Perception by Electrovibration Displayed on Touch Screens
IEEE Transactions on Haptics, 2017
In this study, we investigated the effect of input voltage waveform on our haptic perception of electrovibration on touch screens. Through psychophysical experiments performed with eight subjects, we first measured the detection thresholds of electrovibration stimuli generated by sinusoidal and square voltages at various fundamental frequencies. We observed that the subjects were more sensitive to stimuli generated by square wave voltage than sinusoidal one for frequencies lower than 60 Hz. Using Matlab simulations, we showed that the sensation difference of waveforms in low fundamental frequencies occurred due to the frequency-dependent electrical properties of human skin and human tactile sensitivity. To validate our simulations, we conducted a second experiment with another group of eight subjects. We first actuated the touch screen at the threshold voltages estimated in the first experiment and then measured the contact force and acceleration acting on the index fingers of the subjects moving on the screen with a constant speed. We analyzed the collected data in the frequency domain using the human vibrotactile sensitivity curve. The results suggested that Pacinian channel was the primary psychophysical channel in the detection of the electrovibration stimuli caused by all the square-wave inputs tested in this study. We also observed that the measured force and acceleration data were affected by finger speed in a complex manner suggesting that it may also affect our haptic perception accordingly.
Design of a Tactile Instrument to Measure Human Roughness Perception in a Virtual Environment
IEEE Transactions on Instrumentation and Measurement, 2000
This paper presents the experimental results on the measurement of human texture perception in virtual environments. The experiment is conducted with a haptic tactile instrument that provides sensations of rough textures directly to the fingertip of the users. It consists of a brush and a DC motor. The brush rubs directly against the user's fingertip. Simulated texture is felt through an aperture on the tactile actuator where the users place their fingertip. The speed and direction of the brush are varied to control the roughness of the virtual surface and to determine the effect of either variable on perceived roughness. The actuator is designed to be attached to an existing force feedback device in order to create an interface that can provide force feedback and tactile feedback. The magnitudes of rough textures are measured through this device by comparing the virtual textures with real sandpapers of different grit sizes. Through human factor testing, it is found that the direction of rotation has negligible effects on roughness perception when the time gap between two consecutive stimuli is as large as 10 s. However, when the time gap is reduced to 0.5 s, the effects of direction become prominent. The just noticeable difference with respect to speed is found to decrease as the base speed of the brush increases. The results also show that although each subject's perception of roughness is biased using various sandpapers, the measured data is divided between two trends. One group of users perceives the roughness to increase with increasing speed, while the other group perceives the roughness to decrease.
Virtual Tactile Simulation: A Novel Display and the Effects on Users’ Texture Perception
ASME/ISCIE 2012 International Symposium on Flexible Automation, 2012
This paper presents a novel study on the simulation of material texture by means of electro-tactile stimuli and details the effects on the users' ability to recognize and discriminate different material classes. The research exploits a novel tactile display to simulate material texture and validates the adopted simulation strategy by experimental testing. The tactile system elaborates data from real material samples and combines electrical stimuli and mechanical vibration to reproduce both roughness and texture coarseness sensations. Then, an experimental protocol based on the theory of Psychophysics is defined to carry out system calibration and tests with users. The research aims at validating the proposed simulation strategy and checking the user response on virtual tactile stimuli. Experimentations were carried out to reproduce virtual material texture and measure the users' ability to distinguish different virtual materials and to recognize the material class. Experimental results provide interesting details about tactile perception mechanisms and validate the adopted approach for tactile signals' recognition and material class discrimination.
Audiotactile interactions in roughness perception
Experimental Brain Research, 2002
The sounds produced when we touch textured surfaces frequently provide information regarding the structure of those surfaces. It has recently been demonstrated that the perception of the texture of the hands can be modified simply by manipulating the frequency content of such touch-related sounds. We investigated whether similar auditory manipulations change people's perception of the roughness of abrasive surfaces (experiment 1). Participants were required to make speeded, forced-choice discrimination responses regarding the roughness of a series of abrasive samples which they touched briefly. Analysis of discrimination errors verified that tactile roughness perception was modulated by the frequency content of the auditory feedback. Specifically, attenuating high frequencies led to a bias towards an increased perception of tactile smoothness. In experiment 2, we replicated the rubbing-hands manipulation of previous experimenters while participants rated either the perceived roughness or wetness of their hands. The wetness scale data replicated the results in the literature, while the roughness scale data replicated the result from experiment 1. A final experiment showed that delaying the auditory feedback from the hand-rubbing reduced the magnitude of this parchment-skin illusion. These experiments demonstrate the dramatic effect that auditory frequency manipulations can have on the perceived tactile roughness and moistness of surfaces, and are consistent with the proposal that different auditory perceptual dimensions may have varying salience for different surfaces.
Experimental Brain Research, 2010
A specifically designed force-feedback device accurately simulated textures consisting of lateral forces opposing motion, simulating friction. The textures were either periodic trapezoidal forces, or sinusoidal forces spaced at various intervals from 1.5 mm to 8.5 mm. In each of two experiments, 10 subjects interacted with the virtual surfaces using the index finger placed on a mobile plate that produced the forces. The subjects selected their own speed and contact force for exploring the test surface. The apparatus returned force fields as a function of both the finger position and the force normal to the skin allowing full control over the tangential interaction force. In Experiment #1, subjects used an integer, numerical scale of their own choosing to rate the roughness of eight identical, varyingly spaced force ramps superimposed on a background resistance. The results indicated that subjective roughness was significantly, but negatively, correlated (mean r = -0.84) with the spatial period of the resistances for all subjects. In a second experiment, subjects evaluated the roughness of 80 different sinusoidal modulated force fields, which included 4 levels of resistance amplitude, 4 levels of baseline friction, and 5 spatial periods. Multiple regression was used to determine the relationship between friction, tangential force amplitude, and spatial period to roughness. Together, friction and tangential force amplitude produced a combined correlation of 0.70 with subjective roughness. The addition of spatial period only increased the multiple regression correlation to 0.71. The correlation between roughness estimates and the rate of change in tangential force was 0.72 in Experiment #1 and 0.57 in Experiment #2. The results suggest that the sensation of roughness is strongly influenced by friction and tangential force amplitude, whereas the spatial period of simulated texture alone makes a negligible contribution to the sensation of roughness.
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 [15], 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.