Mechanical Engineering PhD Thesis Defense by Yasemin Vardar






Title: Tactile Perception by Electrovibration


Speaker: Yasemin Vardar


Time: January 11, 2018, 17:00


Place: ENG 208

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

Thesis Committee Members:

Prof. Dr. Cagatay Basdogan (Co-advisor, Koc University)

Prof. Dr. Burak Güçlü (Co-advisor, Boğaziçi University)

Assoc. Prof. Dr. Ipek Basdogan (Koç University)

Prof. Dr. J. Edward Colgate (Northwestern University)

Prof. Dr. Hong Tan (Purdue University)

Asst. Prof. Dr. Evren Samur (Boğaziçi University)



One approach to generating realistic haptic feedback on touch screens is electrovibration. In this technique, the friction force is altered via electrostatic forces, which are generated by applying an alternating voltage signal to the conductive layer of a capacitive touchscreen. Although the technology for rendering haptic effects on touch surfaces using electrovibration is already in place, our knowledge of the perception mechanisms behind these effects is limited. This thesis aims to explore the mechanisms underlying haptic perception of electrovibration in two parts. In the first part, the effect of input signal properties on electrovibration perception is investigated. Our findings indicate that the perception of electrovibration stimuli depends on frequency-dependent electrical properties of human skin and human tactile sensitivity. When a voltage signal is applied to a touchscreen, it is filtered electrically by human finger and it generates electrostatic forces in the skin and mechanoreceptors. Depending on the spectral energy content of this electrostatic force signal, different psychophysical channels may be activated. The channel which mediates the detection is determined by the frequency component which has a higher energy than the sensory threshold at that frequency. In the second part, effect of masking on the electrovibration perception is investigated. We show that the detection thresholds are elevated as linear functions of masking levels for simultaneous and pedestal masking. The masking effectiveness is larger for pedestal masking compared to simultaneous masking. Moreover, our results suggest that sharpness perception depends on the local contrast between background and foreground stimuli, which varies as a function of masking amplitude and activation levels of frequency-dependent psychophysical channels.