Simultaneous Representation of Texture and Geometry on a Flat Touch Surface

Abstract

We propose to combine two types of tactile feedback, electrovibration and mechanical vibration, for haptic interaction on a flat touch surface. This approach would enrich haptic effects for touch screen-based devices by simultaneously providing texture and geometry information.

1 Introduction

Methods for providing haptic feedback on a touch screen have drawn substantial attention. In particular, vibration-based approaches have been studied in depth, since the mechanoreceptors in human skin are sensitive to frequency-dependent vibrotactile stimuli [1]. Numerous studies have been conducted to determine how to provide mechanical vibration feedback to users interacting with touch screens [2], and have demonstrated that the virtual texture created by vibration motors provides the feel of a real textured surface [3]. Electrovibration-based tactile displays have also been proposed in recent years [4]. By modulating the friction forces between a sliding fingertip and a touch screen, electrovibration can display geometry features, such as bumps [5]. However, most previous research has concentrated on creating only textures or geometry features, although both are equally important in simulating real objects. A few researchers have proposed simultaneous geometry and texture display [6, 7]. In this study, we propose to utilize both mechanical vibration and electrovibration for the simultaneous representation of texture and geometry features.

2 System Implementation

The hardware system was constructed as shown in Fig. 1. Electrovibration is produced on a 3M Microtouch panel by applying an electrical signal to the connectors. Mechanical vibration, which is originally generated by piezoelectric haptic actuators (resonant frequency of around 150 Hz) attached to the periphery of the panel, is transmitted to the entire panel. During pilot tests, several combinations of the two feedback types were presented to participants. We observed that users are able to independently perceive mechanical vibration and electrovibration when both feedback types are provided simultaneously.

Fig. 1

Hardware setup for providing electrovibration and mechanical vibration

3 Demonstration

We will demonstrate the proposed method using the hardware setup shown in Fig. 1, with some interactive scenarios. In the demonstration, participants will slide their bare finger on the touch screen in order to interact with a set of virtual objects that vary in texture and geometry. Users can feel not only the surface texture of the virtual objects rendered by mechanical vibration (frequency and amplitude modulation), but also object curvatures rendered by electrovibration (amplitude modulation) [7]. For example, users will be able to clearly discriminate between virtual objects, each of which has different texture (smooth, bumpy, rough, etc.) and shape (cube or sphere), as shown in Fig. 2.

Fig. 2

Examples of demonstration scenarios: a cubes with textures, b spheres with textures