Haptic interfaces for virtual environments: perceived instability and force constancy in haptic sensing of virtual surfaces.

Abstract Haptic interfaces are becoming more commonplace in virtual environment and teleoperation systems. There is a growing need to not only continue to improve hardware platforms and rendering algorithms, but evaluate human performance with haptic interfaces. This review summarizes two recent studies inspired by perception problems in using haptic interfaces to interact with virtual environments. The first study evaluated perceived quality of virtual haptic textures and discovered several types of perceived instability and their sources. We found that the buzzing type of perceived instability was most likely due to the mechanical resonance of the haptic interface hardware, and the aliveness type of perceived instability due to our inability to sense the slight movements of our hands in free space. The second study focused on the motor strategy employed during interaction with a virtual surface via a force-feedback haptic interface. We found that users tended to maintain a constant penetration force into a virtual surface when interacting with the surface. This can result in a reversal in perceived relative surface heights if the taller surface is rendered with a lower stiffness, thereby resulting in an erroneous perception of the virtual environment being rendered. For both studies, possible solutions to improving human perception of virtual and remote objects via hardware and/or software are discussed. Resume Les interfaces haptiques sont de plus en plus communes dans les systemes de realite virtuelle et de teleoperation. Il y a un besoin croissant de continuer non seulement a ameliorer les plateformes materielles et les algorithmes de rendu, mais aussi d'evaluer la performance humaine avec des interfaces haptiques. Cet article resume deux etudes recentes inspirees des problemes de perception signales lors de l'utilisation d'interfaces haptiques pour interagir avec des environnements virtuels. Dans la premiere etude, nous avons evalue la qualite percue des textures haptiques virtuelles et avons decouvert plusieurs types d'instabilite percue et leurs sources. Nous avons constate que le type bourdonnant d'instabilite percue etait vraisemblablement du a la resonance mecanique du materiel de l'interface haptique, et que le type vivant d'instabilite percue etait du a notre incapacite de sentir les legers mouvements de nos mains dans un espace libre. La deuxieme etude portait sur la strategie motrice utilisee durant l'interaction avec une surface virtuelle par le truchement d'une interface haptique a retour de force. Nous avons decouvert que les utilisateurs ont tendance a maintenir une force de penetration constante dans une surface virtuelle lorsqu'ils sont en interaction avec la surface. Cela peut occasionner une inversion des hauteurs relatives percues si la surface la plus elevee est rendue avec une rigidite moindre, entrainant de ce fait une perception erronee de l'environnement virtuel rendu. Nous discutons, pour les deux etudes, des solutions materielles et/ou logicielles possibles pour ameliorer la perception humaine des objets virtuels et distants. To faithfully emulate the feel, as well as the sight and sound, of remote or virtual objects in teleoperation and virtual environments requires multimodal interfaces that match the human sensory and motor capabilities. Over the past two decades, much progress has been made in haptic technologies and in our understanding of the human somatosensory system, both of which are essential to the development of effective and intuitive haptic interfaces that bridge the real and remote/virtual worlds. The state-of-the-art hardware and software systems for haptic virtual environments strive to provide a realistic perceptual experience to enable a user to interact with virtual objects in a natural and intuitive manner. Typical hardware platforms include force-feedback devices such as the PHANToM (SensAble Technologies, Woburn, MA), Omega (Force Dimension, Switzerland), HapticMASTER (MOOG FCS, the Netherlands), MagLev (Berkelman & Hollis, 2000), and ViSHARDlO (Technical University of Munich, Germany) that emulate the exploration and manipulation of objects through a single contact point. …