Sampled- and Continuous-Time Passivity and Stability of Virtual Environments

When digitally realized, virtual environments (VEs) do not perfectly match the physical environments they are supposed to emulate. This paper deals with energy aspects of such a mismatch, i.e., artificial energy leaks. A methodology is developed that employs smooth correction (SC) and leak dissipation (LD) to achieve a stable interconnection of the VE with the haptic device. The SC-LD naturally blends with the original laws for rendering the VE and gives rise to modified force feedback laws. These laws can be regarded as energy-consistent discretizations of their continuous-time counterparts. For some fundamental examples including virtual springs and masses, these laws are analytically reduced to simple closed-form equations. The methodology is then generalized to the multivariable case. Several experiments are conducted including a 2-DOF coupled nonlinear VE example, and a scenario leading to a sequence of contacts with a virtual object. Besides the conceptual advantage, simulation and experimental results demonstrate some other advantages of the SC-LD over well-known time-domain passivity methods. These advantages include improved fidelity, simpler implementation, and less susceptibility to produce impulsive/chattering response.

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Heavy Tails of Discounted Aggregate Claims in the Continuous-Time Renewal Model

Journal of Applied Probability ◽

10.1017/s0021900200002965 ◽

2007 ◽

Vol 44 (02) ◽

pp. 285-294 ◽

Cited By ~ 2

Author(s):

Qihe Tang

Keyword(s):

Asymptotic Formula ◽

Continuous Time ◽

Heavy Tails ◽

Tail Behavior ◽

Renewal Model ◽

Discounted Aggregate Claims ◽

Aggregate Claims ◽

Tail Asymptotic

We study the tail behavior of discounted aggregate claims in a continuous-time renewal model. For the case of Pareto-type claims, we establish a tail asymptotic formula, which holds uniformly in time.

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The sense of presence in virtual environments:

Zeitschrift für Medienpsychologie ◽

10.1026//1617-6383.15.2.69 ◽

2003 ◽

Vol 15 (2) ◽

pp. 69-71 ◽

Cited By ~ 84

Author(s):

Thomas W. Schubert

Keyword(s):

Virtual Environments ◽

Coding Theory ◽

Model Building ◽

Self Report ◽

Survey Study ◽

Spatial Presence ◽

Component Structure ◽

Sense Of Presence ◽

Being There ◽

Measure Sense

Abstract. The sense of presence is the feeling of being there in a virtual environment. A three-component self report scale to measure sense of presence is described, the components being sense of spatial presence, involvement, and realness. This three-component structure was developed in a survey study with players of 3D games (N = 246) and replicated in a second survey study (N = 296); studies using the scale for measuring the effects of interaction on presence provide evidence for validity. The findings are explained by the Potential Action Coding Theory of presence, which assumes that presence develops from mental model building and suppression of the real environment.

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Dreamlike and Playful Virtual Environments to Inspire Children’s Divergent Thinking

Journal of Media Psychology Theories Methods and Applications ◽

10.1027/1864-1105/a000279 ◽

2020 ◽

pp. 1-11

Author(s):

Jérôme Guegan ◽

Claire Brechet ◽

Julien Nelson

Keyword(s):

Virtual Environments ◽

Divergent Thinking ◽

Idea Generation ◽

Combined Processes ◽

Office Environment ◽

School Aged Children

Abstract. Computers have long been seen as possible tools to foster creativity in children. In this respect, virtual environments present an interesting potential to support idea generation but also to steer it in relevant directions. A total of 96 school-aged children completed a standard divergent thinking task while being exposed to one of three virtual environments: a replica of the headmistress’s office, a replica of their schoolyard, and a dreamlike environment. Results showed that participants produced more original ideas in the dreamlike and playful environments than in the headmistress’s office environment. Additionally, the contents of the environment influenced the selective exploration of idea categories. We discuss these results in terms of two combined processes: explicit references to sources of inspiration in the environment, and the implicit priming of specific idea categories.

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