Evren Samur

Data-Driven Texture Rendering with Electrostatic Attraction

In this paper, we present a data-driven haptic rendering method applied to a tactile display based on electrostatic attraction force. For realistic virtual textures, surface data from three materials is collected using an accelerometer and then replayed on the electrostatically-actuated tactile display. The proposed data-driven texture rendering method was compared with the standard square wave excitation through a psychophysical experiment. Subjects rated similarities between real samples and virtual textures rendered by both methods. Results show that the virtual textures generated with the data-driven method had significantly higher percentage of similarity with the real textures in comparison to the square wave signal. In addition, the proposed method resulted in higher number of correct matches between virtual models and real materials.

Data-Driven Texture Rendering on an Electrostatic Tactile Display

ABSTRACT In this article, we present a data-driven texture rendering method applied to a tactile display based on electrostatic attraction. The proposed method was examined in two steps. First, accelerations occurring due to sliding a tool on three different surfaces were measured, and then the collected data were replayed on an electrostatic tactile display. The proposed data-driven texture rendering method was evaluated against a conventional method in which a standard input such as a square wave was used for texture representation. Second, data from the Penn Haptic Texture Toolkit were used to generate virtual textures on the same tactile display. Psychophysical experiments were carried out for both steps, during which subjects rated similarities among the rendered virtual textures and the real samples. Confusion matrices were created, and multidimensional scaling (MDS) analysis was performed to create a perceptual space for further examination and to extract underlying dimensions of the textures. The results show that the virtual textures generated using the data-driven method were similar to the real textures. Roughness and stickiness were the primary dimensions of texture perception. Together with the supporting results from the MDS analysis, this study showed that the data-driven method is a viable solution for realistic texture rendering with electrostatic attraction.

Providing contact sensory feedback for upper limb robotic prosthesis

Lack of the sense of touch is the fundamental problem of todays robotic prostheses. Considering the fact that touch feedback plays a significant role on identifying contacted objects, our aim in this study is to use acceleration signals, occurring due to physical contact of a prosthetic hand with objects, as sensory feedback. We apply these signals on the clavicle bone using a tactor as a haptic interface. First, a library of the acceleration signals occurring as a result of tapping on different materials is collected. Effect of the impact velocity is studied and used as a scalar for real-time applications. In order to model the contact accelerations, a stochastic signal model is developed. Due to the distinct waveform characteristics of different materials, frequency and amplitude of the acceleration signals, together with the impact velocity, are used to identify stiffness of the objects. In a real-time experiment, performed using a robotic finger, the whole procedure of recording, identifying and replaying the signals by the tactor is studied. The preliminary results show that the tactor is able to provide distinguishable feelings of hard and soft objects to the user.

Topologically optimised flexure hinge based XY stage

The purpose of this study is to develop a millimeter scale two degree of freedom planar actuation mechanism (XY stage) with flexure hinges that can generate micrometer scale motion at high frequencies. To amplify the micro scale motion in X and Y directions, two identical levers are used. According to the analytical and computational results, a prototype is developed for validation. Piezoelectric actuators are used in the system because of their compactness and large force capacity. The levers in the XY stage are topologically optimized so that the first resonance frequency of the system is maximized, which enlarges the operation range of the system.

Real-Time Contact Sensory Feedback for Upper Limb Robotic Prostheses

Lack of sense of touch is a fundamental problem for todays robotic prostheses. Considering that touch feedback plays a significant role in identifying contacted objects, the aim of this study is to use acceleration signals, which occur due to physical contact of a prosthetic hand with objects, as sensory feedback. These contact signals are applied on the clavicle bone using a tactor. First, a library of accelerations occurring as a result of tapping on different materials is prepared. The effect of impact speed is studied and used as a scaler for real-time applications. A stochastic signal model is developed for the contact accelerations. Due to the distinct waveform characteristics of different materials, the rate of change of acceleration is used to identify hardness of the objects. In a psychophysical study, the whole procedure of recording, identifying, and replaying the signals is investigated. Results of this study showed the ability of the designed tactor to provide distinguishable hardness sensations of different materials in real time. Furthermore, considering the results of the position control test with and without vision, it can be concluded that the proposed contact sensory feedback method could be enough to substitute for vision during simple grasping tasks.

On Generation of Active Feedback with Electrostatic Attraction

In this study, an active electrostatic tactile display, which is capable of applying directional forces to a stationary finger, is analyzed. Directional forces are created using friction induced by electrostatic attraction. A shaker is used to move the tactile display relative to the stationary finger. In order to investigate the factors affecting active feedback such as relative displacement, frequency of excitation signal and amplitude of the excitation signal, a combination of signals is implemented. In the first step, minimum relative displacement necessary for directional force is examined. In the second step, lateral forces are measured for four distinct frequencies of electrostatic excitation. Finally in the third step, the effect of the amplitude of excitation voltage is investigated. The results show the feasibility of creating active feedback on an electrostatic tactile display. Minimum relative displacement is found as 4 mm. Increasing frequency and amplitude of electrostatic signal lead to the higher value of the directional force.