FORCETAB: VISUO-HAPTIC INTERACTION WITH AFORCE-SENSITIVE ACTUATED TABLET Jens Maiero *,† , Ernst Kruijff * , Andr´ e Hinkenjann * , Gheorghita Ghinea † * Institute of Visual Computing, Bonn-Rhein-Sieg University of Applied Sciences, Germany † Department of Computer Science, Brunel University, United Kingdom {jens.maiero, ernst.kruiff, andre.hinkenjann}@h-brs.de, george.ghinea@brunel.ac.uk Fig. 1: Interaction concept of ForceTab (black the current state of the system and gray the previous one) (a) 2D finger position to elevation, (b) finger force to change a state and (c) continues finger position and force tracking to map physical object properties. ABSTRACT Enhancing touch screen interfaces through non-visual cues has been shown to improve performance. In this paper we report on a novel system that explores the usage of a force- sensitive motion-platform enhanced tablet interface to im- prove multi-modal interaction based on visuo-haptic instead of tactile feedback. Extending mobile touch screen with force-sensitive haptic feedback has potential to enhance per- formance interacting with GUIs and to improve perception of understanding relations. A user study was performed to de- termine the perceived recognition of different 3D shapes and the perception of different heights. Furthermore, two appli- cation scenarios are proposed to explore our proposed visuo- haptic system. The studies show the positive stance towards the feedback, as well as the found limitations related to per- ception of feedback. Index Terms— Touchscreen interaction, haptics, visuo- haptic feedback 1. INTRODUCTION Touch screen interfaces have become a widespread commod- ity, enabling a wide variety of applications through estab- lished interaction styles. These interaction styles afford finger or pen-based interaction with a multitude of graphical user in- terface (GUI) elements. Often, interaction is aided by audio and simple vibro-tactile (pseudo-haptic) cues, which has been shown to enhance performance [1]. While apt for many ap- plications, interest is growing to also explore other directions, including haptic and more advanced pseudo-haptic feedback. However, in particular the combination of haptics and touch screen interaction has not been widely studied and is still chal- lenging. For example, sensing the shape of an underlying ge- ometry like a button is still hard to support. In this paper, we present ForceTab, a system that explores the potential of haptic cues in touch screen interaction (see Figure 1). The system deploys a motion-platform enhanced tablet interface that has been extended with pressure sensors to sense fin- ger pressure (see Figure 2). While related systems without pressure sensing exist, an in-depth analysis of actuated tablet interaction techniques, with and without pressure support, is lacking. In this paper, we advance beyond the state of art by presenting and validating a refined set of feedback mecha- nisms tailored to the abilities of the motion-platform. In par- ticular, the pressure sensor extension allows for a wider range of haptic events to be triggered. Furthermore, in contrast to previously used 1 degree of freedom (DOF) movements [2] our approach also supports inclination, according to the posi- tion and the underlying geometry. Since most available touch screens are capacitive, capturing finger pressure is challeng- ing unless additional techniques are applied [3]. ForceTab presents the potential of visuo-haptic devices by exploring the detection rate of different, static and dynamic, 3D geometries. To do so, we introduce a velocity guided detection approach, to determine a relationship between velocity, shapes and de- tection. Through a set of user studies, we report on both the low-level potential and limitations of the feedback methods to elicit shapes, and show how visuo-haptic feedback can be deployed through two application scenarios.