Yiannis E. Papelis

HCSM: a framework for behavior and scenario control in virtual environments

This paper presents HCSM, a framework for behavior and scenario control based on communicating hierarchical, concurrent state machines. We specify the structure and an operational execution model of HCSMs state machines. Without providing formal semantics, we provide enough detail to implement the state machines and an execution engine to run them. HCSM explicitly marries the reactive (or logical) portion of system behavior with the control activities that produce the behavior. HCSM state machines contain activity functions that produce outputs each time a machine is executed. An activity functions output value is computed as a function of accessible external data and the outputs of lower-level state machines. We show how this enables HCSM to model behaviors that involve attending to multiple concurrent concerns and arbitrating between conflicting demands for limited resources. The execution algorithm is free of order dependencies that cause robustness and stability problems in behavior modeling. In addition, we examine the problems of populating virtual environments with autonomous agents exhibiting interesting behavior and of authoring scenarios involving such agents. We argue that HCSM is well suited for modeling the reactive behavior of autonomous agents and for directing such agents to produce desired situations. We demonstrate use of HCSM for modeling vehicle behavior and orchestrating scenarios in the Iowa Driving Simulator, an immersive real-time virtual driving environment.

The Iowa Driving Simulator: an immersive research environment

This simulators rich, fully interactive environment provides varied scenarios for meeting experimental needs-for example, engineering evaluation of automated highway systems. >

THE IOWA DRIVING SIMULATOR : AN IMPLEMENTATION AND APPLICATION OVERVIEW

This paper gives an overview of the Iowa Driving Simulator (IDS) designed to create high fidelity, operator-in-the-loop vehicle simulation and realistic cueing feedback to the driver. The paper refers to a number of human factors issues that are currently being investigated. Focus is on two specific applications of the IDS: a study of Automated Highway Systems (AHS) and vehicle virtual prototyping on a virtual proving ground.

Driving simulation: challenges for VR technology

Virtual driving environments represent a challenging test for virtual reality technology. We present an overview of our work on the problems of scenario and scene modeling for virtual environments (VEs) in the context of the Iowa Driving Simulator (IDS). The requirements of driving simulation-a deterministic real-time software system that integrates components for user interaction, simulation, and scenario and scene modeling-make it a valuable proving ground for VE technologies. The goal of our research is not simply to improve driving simulation, but to develop technology that benefits a wide variety of VE applications. For example, our work on authoring high-fidelity VE databases and on directable scenarios populated with believable agents also targets applications involving interaction with simulated, walking humans and training in the operation of complex machinery. This work has benefited greatly from the experience of developing components for a full-scale operational VE system like IDS, and we believe that many other proposed VE technologies would similarly benefit from such real-world testing.

Specification and analysis of parallel/distributed software and systems by Petri nets with transition enabling functions

An approach for visually specifying parallel/distributed software using Petri nets (PNs) extend with transition enabling functions (TEFs) is investigated. The approach is demonstrated to be useful in the specification of decision-making activities that control distributed computing systems. PNs are employed because of their highly visual nature that can give insight into the nature of the controller of such a system and because of their analytical properties. In order to increase the expressive power of PNs, the extension of TEFs is used. The main focus is the specification and analysis of parallel/distributed software and systems. A key element of this approach is a set of rules derived to automatically transform such an extended net into a basic PN. Once the rules have been applied to transform the specification, analytical methods can be used to investigate characteristic properties of the system and validate correct operation. >

An Epidemiological Model of Rift Valley Fever with Spatial Dynamics

As a category A agent in the Center for Disease Control bioterrorism list, Rift Valley fever (RVF) is considered a major threat to the United States (USA). Should the pathogen be intentionally or unintentionally introduced to the continental USA, there is tremendous potential for economic damages due to loss of livestock, trade restrictions, and subsequent food supply chain disruptions. We have incorporated the effects of space into a mathematical model of RVF in order to study the dynamics of the pathogen spread as affected by the movement of humans, livestock, and mosquitoes. The model accounts for the horizontal transmission of Rift Valley fever virus (RVFV) between two mosquito and one livestock species, and mother-to-offspring transmission of virus in one of the mosquito species. Space effects are introduced by dividing geographic space into smaller patches and considering the patch-to-patch movement of species. For each patch, a system of ordinary differential equations models fractions of populations susceptible to, incubating, infectious with, or immune to RVFV. The main contribution of this work is a methodology for analyzing the likelihood of pathogen establishment should an introduction occur into an area devoid of RVF. Examples are provided for general and specific cases to illustrate the methodology.

An empirical study of the effectiveness of electronic stability control system in reducing loss of vehicle control.

A significant percentage of fatal vehicle crashes involve loss of control (LOC). Electronic stability control (ESC) is an active safety system that detects impending LOC and activates counter-measures that help the driver maintain or re-gain control. To assess the effectiveness of ESC in preventing LOC, an empirical study was conducted on a high-fidelity driving simulator. The ESC systems for two vehicles were incorporated into the simulators dynamics code which was calibrated to ensure engineering validation. The study utilized three scenarios designed to recreate typical LOC situations, and was designed to assess the effects of ESC presence, vehicle type, scenario, age and gender. A total of 120 research participants completed the study. Results showed a statistically significant reduction in LOC with ESC compared to without ESC (F=52.72, p<0.0001). The study findings of 5% LOC with ESC and 30% without ESC match several epidemiological studies that have analyzed ESC effectiveness on real-world crashes, providing strong support to the use of driving simulation for studying driver behavior. Study conclusions suggest that wide-spread utilization of ESC is likely to reduce traffic fatalities.

Mathematical Model to Assess the Relative Effectiveness of Rift Valley Fever Countermeasures

Mathematical modeling of infectious diseases is increasingly used to explicate the mechanics of disease propagation, impact of controls, and sensitivity of countermeasures. The authors demonstrate use of a Rift Valley Fever (RVF) model to study efficacy of countermeasures to disease transmission parameters. RVF is a viral infectious disease that propagates through infected mosquitoes and primarily affects animals but also humans. Vaccines exist to protect against the disease but there is lack of data comparing efficacy of vaccination with alternative countermeasures such as managing mosquito population or destroying infected livestock. This paper presents a compartmentalized multispecies deterministic ordinary differential equation model of RVF propagation among livestock through infected Aedes and Culex mosquitoes and exercises the model to study the efficacy of vector adulticide, vector larvicide, livestock vaccination, and livestock culling on livestock population. Results suggest that livestock vaccination and culling offer the greatest benefit in terms of reducing livestock morbidity and mortality.

A vehicle-terrain system modeling and simulation approach to mobility analysis of vehicles on soft terrain

This paper presents an approach to modeling and simulation of vehicles interacting with the environment (terrain) in a realistic, three-dimensional setting and to assess vehicle mobility based on simulation results. To reliably predict vehicle performance under realistic off-road conditions, lumped-parameter models commonly used in vehicle dynamics are not adequate. In this work, high fidelity, multibody dynamics approach is employed to capture vehicle nonlinear dynamic characteristics. Because all vehicle control forces/moments are generated at the patch where tire and terrain interacts, tire modeling, soil modeling, and tire-soil interaction modeling are critical. In this work, tire is modeled as multiple-input-multiple-output system with parameters determined via high-fidelity physical-based finite element model and/or test data; soil is modeled using the Bekker-Wong approach with parameters determined using high-fidelity physical-based finite element soil model and/or test data. Although the Bekker-Wong approach is relatively old, effective implementation to achieve its fully potential is possible only recently, with the advent of the so-called dynamic terrain database. A computational algorithm for such an implementation is presented. Dynamic terrain allows natural treatment of the multiple-pass problem in spatial and dynamic fashion, as opposed to the approaches found in the literature that can only deal with planar, steady-state rolling in an ad hoc fashion. Tire-terrain interaction is modeled using a hybrid approach of empirical and semi-empirical models. A complete simulation environment can be constructed by integrating all the models and mobility analysis of vehicles be perform on soft terrain. An example is presented to demonstrate the approach. Conclusions and future research directions are presented at the end of the paper.

An agent-based crowd behaviour model for real time crowd behaviour simulation

We propose an agent-based/flow-field/aggregate dynamics crowd behaviour model.We measure the performance of our model.We assess the qualitative results of our model. Crowd behaviour models are divided into agent-based, flow-based and particle-based in terms of whether the behaviour emerges from simulating all people (agents) individually (Koh and Zhou, 2011; Braun et al., 2005; Luo et al., 2008; Pan et al., 2007; Shendarkar et al., 2006; Narain et al., 2009), is programmatically defined a priori using fluid dynamics models (Hughes, 2002, 2003; He et al., 2011), or employ a particle system governed by physical laws (Helbing et al., 2000; Bouvier et al., 1997; Treuille et al., 2006; Cucker and Smale, 2007). In agent-based models, computationally intense problems, such as global navigation, hinder the efficient real-time modelling of thousands of agents. In this paper we present a novel approach to crowd behaviour modelling which couples the agent-based paradigm of allowing high level of individual parametrization (group behaviour between friends, leader/follower individuals) with an efficient approach to computationally intensive problems encountered in very large number of agents thus enabling the simulation of thousands of agents in real time using a simple desktop PC.