MAPS (Multimodal Application for the Perception of Spaces) is a tablet App, with associated hardware, for providing on-the-go access to audio-tactile maps of unfamiliar indoor venues to individuals who are blind or visually impaired. Performance of the system was assessed using a survey knowledge task in which participants were exposed to three different cue combinations: audio only, audio with haptic cues provided by the tablet--s built-in vibrational motor (built-in tactile), and audio with haptic feedback provided by special vibrating rings worn on two fingers (stereo-tactile). Of the three conditions, the combination of audio and built-in tactile feedback resulted in superior user performance in judging the relative direction to points of interest. Results indicate that the audio-tactile display improves survey knowledge both when used for a priori (pre-visit) map learning and on-the-go (within the environment) to provide just-in-time information.

Vibration motors are often used to generate tactile effects by exciting a mass at a given frequency and amplitude. The characteristic impedance of this vibrotactile device is not always in harmony with the impedance of the human skin. This impedance mismatch can result in poor energy transfer, necessitating larger motors and greater power consumption than otherwise required. Herein, we investigate the feasibility of improving the energy transfer by placing a medium between the skin and the motor, which we dub an impedance adapter. We simulate the effects of this impedance adapter using a mathematical model, and evaluate its effect on skin displacement and a parameter we call skin stimulus. Skin stimulus is introduced as a measure of the perceptive effects of a haptic system, and is used to compare results between systems with an impedance adapter and those without. Our findings suggest a factor of four improvement in skin displacement and a two-fold increase in skin stimulus are possible by introducing an optimized impedance adapter.

Vibrotactile devices suffer from poor energy efficiency, arising from a mismatch between the device and the impedance of the human skin. This results in over-sized actuators and excessive power consumption, and prevents development of more sophisticated, miniaturized and low-power mobile tactile devices. In this paper, we present the experimental evaluation of a vibrotactile system designed to match the impedance of the skin to the impedance of the actuator. This system is able to quadruple the motion of the skin without increasing power consumption, and produce sensations equivalent to a standard system while consuming 1/2 of the power. By greatly reducing the size and power constraints of vibrotactile actuators, this technology offers a means to realize more sophisticated, smaller haptic devices for the user interface community.

In the task-saturated environment of extravehicular activity (EVA), an astronaut's ability to leverage suit-integrated information systems is limited by a lack of options for data entry. In particular, bulky gloves inhibit the ability to interact with standard computing interfaces such as a mouse or keyboard. This paper presents the results of a preliminary investigation into a system that permits the space suit gloves themselves to be used as data entry devices. Hand motion tracking is combined with simple finger gesture recognition to enable use of a virtual keyboard, while tactile feedback provides touch-based context to the graphical user interface (GUI) and positive confirmation of keystroke events. In human subject trials, conducted with twenty participants using a prototype system, participants entered text significantly faster with tactile feedback than without (p = 0.02). The results support incorporation of vibrotactile information in a future system that will enable full touch typing and general mouse interactions using instrumented EVA gloves.

Creating a compelling haptic sense of immersion in a virtual environment is a challenging task for the control engineer. A haptic display must render both low impedance free-space motion and high impedance rigid constraints while ensuring stable interaction. This paper outlines a control design approach for the most common haptic display implementation, the impedance display. Two-port absolute stability criteria are used to develop explicit design bounds for virtual coupling networks which guarantee system stability for a broad class of human operators and virtual environments. The technique is applied to the Excalibur three-axis force display. The resulting absolutely stable haptic interface is the centerpiece of a virtual building block simulation which emulates the behavior of LEGO/sup TM/ bricks in a virtual environment.

This paper addresses fundamental stability and performance issues associated with haptic interaction. It generalizes and extends the concept of a virtual coupling network, an artificial link between the haptic display and a virtual world, to include both the impedance and admittance models of haptic interaction. A benchmark example exposes an important duality between these two cases. Linear circuit theory is used to develop necessary and sufficient conditions for the stability of a haptic simulation, assuming the human operator and virtual environment are passive. These equations lead to an explicit design procedure for virtual coupling networks which give maximum performance while guaranteeing stability. By decoupling the haptic display control problem from the design of virtual environments, the use of a virtual coupling network frees the developer of haptic-enabled virtual reality models from issues of mechanical stability.

A haptic interface is a kinesthetic link between a human operator and a virtual environment. This paper addresses stability and performance issues associated with haptic interaction. It generalizes and extends the concept of a virtual coupling network, an artificial connection between a haptic display and a virtual world, to include both the impedance and admittance models of haptic interaction. A benchmark example exposes an important duality between these two cases. Linear circuit theory is used to develop necessary and sufficient conditions for the stability of a haptic simulation, assuming the human operator and virtual environment are passive. These equations lead to an explicit design procedure for virtual coupling networks which give maximum performance while guaranteeing stability. By decoupling the haptic display control problem from the design of virtual environments, the use of a virtual coupling network frees the developer of haptic-enabled virtual reality models from issues of mechanical stability.