86 A Large Workspace Haptic Device For Human-Scale Virtual Environments Laroussi Buoguila P&I, Tokyo Institute of Technology 4259 Nagatsuta, Midori ku, 226-8503 Yokohama - Japan Phone: +81 45 924 5050 laroussi@pi.titech.ac.jp Masahiro Ishii P&I, Tokyo Institute of Technology 4259 Nagatsuta, Midori ku, 226-8503 Yokohama - Japan Phone: +81 45 924 5050 mishii@pi.titech.ac.jp Makoto Sato P&I, Tokyo Institute of Technology 4259 Nagatsuta, Midori ku, 226-8503 Yokohama - Japan Phone: +81 45 924 5050 msato@pi.titech.ac.jp ABSTRACT The paper aims to present a new human-scale haptic device for virtual environment named Scaleable-SPIDAR (Space Interface Device for Artificial Reality), which can provides different aspects of force feedback sensations, associated mainly with weight, contact and inertia, to both hands within a cave-like space. Tensioned string techniques are used to generate such haptic sensations, while keeping the space transparent and unbulky. The device is scaleable so as to enclose different cave-like working space. Scaleable-SPIDAR is coupled with a large screen where a computer generated virtual world is displayed. The used approach is shown to be simple, safe and sufficiently accurate for human-scale virtual environment. Keywords Human-Scale, Virtual Environment, Force Feedback. 1. INTRODUCTION The uses of high quality computer-generated imagery, auditory and interactive scenes have recently been applied to many cave-like virtual environments. Accurate simulations and graphical display of these virtual environments are being used to impart users with realistic experiences. As well as, to provide a more comprehensive understanding of specific problems. However, visual and auditory cues alone do not allow the user to clearly perceive and understand physical interactions such as contact, pressure and weight. The importance of such sensory modality in virtual workspace had already been showed in many researches. To create an immersible human-scale virtual environment, the ability to interact physically with virtual environment, as well as the full and direct use of both hands are indispensable to control over objects and to develop a physical skill. However, to provide such capability of perception and action in a human-scale virtual environment, usually some mechanical equipment attached to a stationary ground as well as to the operator’s body are required [7]. This direct contact between hard equipment and operator limits the range of movement and may occlude the graphical display. As well, the weight and the bulk of the mechanical attachments are clearly perceived by the operator, figure 1. Although GROPE-project [1] may be the most famous human-scale virtual environment system with force display. Yet, most of the current haptic devices are designed for desktop usage and display force feedback to only one hand. Unlike video and audio, force information is very difficult to send through air. To form a 3D force at a certain point, say point A, lead a “hard” mechanical device from a “force source” to point A may be the only “simple” and precise way. If A is moveable, then the force display device will become much more complicated in structure compared with video and audio display. Particularly, when the virtual environment workspace becomes larger, that is the point A may go far away from the force source, the haptic device structural strength needs to be enhanced to keep the precision. This enhancement usually makes the whole system bulky, heavy and expensive, as well limits the user’s moving freedom. On the other hand, the machinery based forces displays are usually low dynamic performance. In a mechanical system, the dynamic performance is mainly decided by system’s weight and moment of inertia. As the haptic devices in human-scale virtual environment are heavy, they would have lower dynamic performance than the ones in a relatively small system, desktop devices. Unfortunately, the task in large working space tends to need higher moving speed and bigger acceleration. How to balance precision and dynamic performance? While improving both of them are the key points to realize usable and accurate force display in human-scale virtual environment. We propose a new approach, based on tensioned string techniques, to display force feedback sensation on both operator's hands in a large space. While allowing smooth movement and keeping the space transparent. In the next sections, we explain the features of Scaleable-SPIDAR. A trial system was developed and tested through experiments. Additionally, an application was developed to evaluate the profitability of our device. In the last section, the remaining problems are discussed. 2. CONCEPT OF SCALEABLE-SPIDAR The device is derived from the original desktop SPIDAR device, which was introduced late in 1990 by Makoto Sato et al [3]. As shown in figure 2, Scaleable-SPIDAR is delimited by a cubic frame that enclose a cave-like space, where the operator can move around to perform large scale movements. The experimental prototype is 27m 3 size (3m x 3m x 3m). Within this space, different aspect of force feedback sensations associated mainly with weight, contact and inertia can be displayed to the operator’s hands by means of tensioned strings. The front side of the device holds a large screen, where a computer-generated virtual world is projected. Providing Desk Attachment Figure 1: Typical mechanical attachment Ceiling attachment A A