Destination Area: Intelligent Infrastructure for Human-Centered Communities (IIHCC)
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IIHCC focuses its attention on the ways that people interact with one another and with their environment. Interest areas in this DA include smart, healthy, and sustainable cities and communities; transportation systems; human safety, health, and wellness; integrated energy systems; network science and engineering; public policy; and cyber-physical systems. The initial focus for IIHCC will be on four themes:
Ubiquitous Mobility: The location-agnostic promise of new communication and information technologies
Automated Vehicle Systems: vehicles that can transit safely and efficiently through our communities independent of a human operator
Smart Design and Construction: an intelligent, integrated, adaptable, responsive, and sustainable human-centric built environment
Energy: the underlying innovations that will be required in the production, distribution, and consumption of energy to realize such a system
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Browsing Destination Area: Intelligent Infrastructure for Human-Centered Communities (IIHCC) by Content Type "Technical report"
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- Automated Vehicle Crash Rate Comparison Using Naturalistic DataBlanco, Myra; Atwood, Jon; Russell, Sheldon M.; Trimble, Tammy E.; McClafferty, Julie A.; Perez, Miguel A. (Virginia Tech Transportation Institute, 2016-01-08)This study assessed driving risk for the United States nationally and for the Google Self-Driving Car project. Driving safety on public roads was examined in three ways. The total crash rates for the Self-Driving Car and the national population were compared to (1) rates reported to the police, (2) crash rates for different types of roadways, and (3) scenarios that give rise to unreported crashes. First, crash rates from the Google Self-Driving Car project per million miles driven, broken down by severity level were calculated. The Self-Driving Car rates were compared to rates developed using national databases which draw upon police-reported crashes and rates estimated from the Second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study (NDS). Second, SHRP 2 NDS data were used to calculate crash rates for three levels of crash severity on different types of roads, broken down by the speed limit and geographic classification (termed “locality” in the study; e.g., urban road, interstate). Third, SHRP 2 NDS data were again used to describe various scenarios related to crashes with no known police report. This analysis considered whether such factors as driver distraction or impairment were involved, or whether these crashes involved rear-end collisions or road departures. Crashes within the SHRP 2 NDS dataset were ranked according to severity for the referenced event/incident type(s) based on the magnitude of vehicle dynamics (e.g., high Delta-V or acceleration), the presumed amount of property damage (less than or greater than $1,500, airbag deployment), knowledge of human injuries (often unknown in this dataset), and the level of risk posed to the drivers and other road users (Antin, et al., 2015; Table 1). Google Self-Driving Car crashes were also analyzed using the methods developed for the SHRP 2 NDS in order to determine crash severity levels and fault (using these methods, none of the vehicles operating in autonomous mode were deemed at fault in crashes).
- Control-Oriented Planar Motion Modeling of Unmanned Surface VehiclesSonnenburg, C.; Gadre, Aditya; Horner, D.; Krageland, S.; Marcus, A.; Stilwell, Daniel J.; Woolsey, Craig A. (Virginia Center for Autonomous Systems, 2010)This technical report describes a comparison of experimentally identified dynamic models for the planar motion of an unmanned surface vehicle (USV). The objective is to determine a model which is (1) sufficiently rich to enable effective model-based control design, (2) sufficiently simple to allow straight forward parameter identification, and (3) sufficiently general to apply to a variety of hullforms and actuator configurations. Starting from a three degree-of-freedom nonlinear model obtained from physical principles, we consider five simplified variants that include four linear models and two nonlinear models for low speed operation. The first linear model comes from linearizing the full planar boat dynamics about a straight constant speed. A first order steering model relates steering angle to turn rate. A second order steering model relates steering angle to turn rate and sideslip angle. A first order speed model relates throttle setting to forward speed. The two nonlinear models are derived from potential flow around a simple shape. Linear damping and quadratic damping are included in each nonlinear model respectively. To identify parameters for these models, data must be collected that show the dynamic and steady-state relationships between inputs and outputs. Using these data sets, simple models that satisfy the three given criteria are identified for three types of unmanned surface vehicle: a rigid hull inflatable boat with an outboard engine, a rigid hull inflatable boat with a waterjet propulsion system, and a small pontoon boat with two electric thrusters.
- Dynamics & Control of Underwater Gliders II: Motion Planning and ControlMahmoudian, N.; Woolsey, Craig A. (Virginia Center for Autonomous Systems, 2010)This paper describes an underwater glider motion control system intended to enhance locomotive efficiency by reducing the energy expended by vehicle guidance and control. In previous work, the authors derived an approximate analytical expression for steady turning motion by applying regular perturbation theory to a sophisticated vehicle dynamic model. Using these steady turn solutions, including the special case of wings level glides, one may construct feasible paths for the gliders to follow. Because the turning motion results are only approximate, however, and to compensate for model and environmental uncertainty, one must incorporate feedback to ensure precise path following. This report describes the development and numerical implementation of a feedforward/feedback motion control system for a multi-body underwater glider model. Since the motion control system relies largely on steady motions, it is intrinsically efficient. Moreover, the nature of the steady turn approximations suggests a method for nearly energy-optimal path planning.
- Dynamics and Control of Underwater Gliders I: Steady MotionsMahmoudian, N.; Geisbert, J.; Woolsey, Craig A. (Virginia Center for Autonomous Systems, 2007)This paper describes analysis of steady motions for underwater gliders, a type of highly efficient underwater vehicle which uses gravity for propulsion. Underwater gliders are winged underwater vehicles which locomote by modulating their buoyancy and their attitude. Several such vehicles have been developed and have proven their worth as efficient long-distance, long-duration ocean sampling platforms. To date, the primary emphasis in underwater glider development has been on locomotive efficiency; maneuverability has been a secondary concern. The ultimate aim of our research is to develop optimal motion control strategies which enhance the natural locomotive efficiency of underwater gliders by minimizing the energy expended by the control system. Ambitious applications such as persistent undersea surveillance require not only efficient vehicles, but efficient guidance and control schemes. This technical report aims to develop a better understanding of glider maneuverability, particularly with regard to turning motions. As a preliminary step, we develop an approximate analytical expression for steady turning motion for a realistic glider model. The problem is formulated in terms of regular perturbation theory, with the vehicle turn rate as the perturbation parameter. The resulting solution exhibits a special structure that allows one to apply existing optimal path planning results for planar mobile robots. The ultimate result is a simple, energy-efficient motion control method for underwater gliders.
- Infrastructure Pavement Assessment & Management Applications Enabled by the Connected Vehicles Environment – Proof-of-ConceptFlintsch, Gerardo W.; Smith, Brian L. (Research and Innovative Technology Administration, 2015-09-30)The objective of this project was to develop prototypes and conduct a field test of system level applications of a connected vehicle pavement condition measurement system. This allowed the research team to: (1) investigate different approaches to a connected vehicle pavement measurement system; and (2) determine the optimum procedures for collecting, processing, aggregating, and storing the data to support engineering and management decisions. The study found that roughness measures obtained from probe vehicles are comparable to roughness measures obtained from the profile, when the appropriate parameters that affect roughness were taken into account. A sensitivity analysis suggested that data sampling and quarter-car parameters were the most critical parameters. Finally, the results of the network-level simulations showed that the probe vehicle vertical acceleration measurements (collected from a mobile smart phone application) have the potential to be used for network-level prescreening of deficient pavement sections.
- Intersection Decision Support: Evaluation of a Violation Warning System to Mitigate Straight Crossing Path CollisionsNeale, Vicki L.; Perez, Miguel A.; Doerzaph, Zachary R.; Lee, Suzanne E.; Stone, Scott R.; Dingus, Thomas A. (Virginia Center for Transportation Innovation and Research, 2006-04)This project entailed the design, development, testing, and evaluation of intersection decision support (IDS) systems to address straight crossing path (SCP) intersection crashes. This type of intersection crash is responsible for more than 100,000 crashes and thousands of fatalities each year. In developing these IDS systems for both signalized and stop-controlled intersections, a top-down systems approach was used that determined the necessary system functions and evaluated the capability of different technologies to perform those functions. Human factors tests were also conducted that evaluated the effectiveness of warning algorithms and infrastructure-based driver-infrastructure interfaces in eliciting a stopping response from drivers about to be involved in an SCP intersection crash. Results indicated that further technological development is needed for the sensing and intersection state IDS functions. Furthermore, infrastructure-based warning interfaces tested were greatly outperformed by previously-tested in-vehicle warnings. Thus, future research on IDS systems should focus on their infrastructure-cooperative configuration, where the system supports an in-vehicle warning.
- Nonlinear Estimation with State-Dependent Gaussian Observation NoiseSpinello, D.; Stilwell, Daniel J. (Virginia Center for Autonomous Systems, 2008)We consider the problem of estimating the state of a system when measurement noise is a function of the system's state. We propose generalizations of the iterated extended Kalman filter and of the extended Kalman filter that can be utilized when the state estimate distribution is approximately Gaussian. The state estimate is computed by an iterative root-searching method that maximize a maximum likelihood function. For sensor network applications, we also address distributed implementations involving multiple sensors.
- Optimal Control of an Undersea Glider in a Symmetric Pull-upKraus, R.; Cliff, Eugene M.; Woolsey, Craig A.; Luby, J. (Virginia Center for Autonomous Systems, 2008)An undersea glider is a winged autonomous undersea vehicle which modulates its buoyancy to rise or sink and moves its center of mass to control pitch and roll attitude. By properly phasing buoyancy and pitch control, an undersea glider rectifies the vertical motion caused by changes in buoyancy into forward motion caused by the lift force on the fixed wing. The characteristic "porpoising" motion is useful in oceanographic surveys and the propulsion method is extremely efficient - undersea gliders routinely operate for months without human intervention. Glider efficiency could be improved even further by addressing the phenomenon of "stall" (loss of lift) when a glider transitions from downward to upward flight. Because the stall phenomenon occurs asymmetrically over the vehicle's wing, it can cause directional errors which must be corrected at a corresponding energetic cost. This paper describes the formulation of a point mass model and its dynamic equations of motion. An optimal control formulation was designed using angle of attack and buoyancy as controls to investigate control scheduling methods for avoiding stall in a symmetric pull-up. The calculations were repeated using three different numerical solution techniques for comparison of the methodologies and results. The model was updated to include longitudinal rigid body dynamics and changed the control to the rate of change of the longitudinal center of gravity location. This model allowed for the inclusion of added mass effects due to fluid displacement.
- Safety, Operational, and Energy Impacts of In-vehicle Adaptive Stop Displays Using Connected Vehicle TechnologyNoble, Alexandria M. (Connected Vehicle/Infrastructure University Transportation Center (CVI-UTC), 2015-07-30)Un-signalized intersections create multiple opportunities for missed or misunderstood information. Stop sign-controlled intersections have also been shown to be a source of delay and emissions due to their frequent, often inappropriate use. By using connected vehicle technology, it is possible to place electronic stop signs at more conspicuous locations that can communicate with the in-vehicle systems. Then, if a conflict is imminent at an intersection, the vehicle’s system alerts the driver, thus reducing the probability of missed information, as well as decreasing the amount of unnecessary delay, fuel consumption, and emissions by only prompting a stop when a conflict is present. Before implementing any new technology, it is important to assess it from both a transportation engineering and human factors standpoint to determine the value of such a system. The objective of this study was to assess perceived benefits of an adaptive in-vehicle stop display and to determine if there were any negative safety implications with the use of this system. This was accomplished through a test track experiment with 49 participants. These drivers were presented with a standard R1-1 stop sign on the in-vehicle display, as well as an experimental sign, which informed them to proceed through the intersection with caution. Results indicate the implementation of this technology reduces delay, decreases fuel consumption, and does not instigate any safety decrements.
- Sensor Error Model for a Uniform Linear ArrayGadre, Aditya; Roan, Michael J.; Stilwell, Daniel J. (Virginia Center for Autonomous Systems, 2008)We derive a measurement error model for a uniform linear array whose output is the bearing to a single narrowband acoustic source. The measurement error depends on various array as well as environmental parameters, which include the number of hydrophones in the array, spacing between adjacent hydrophones, frequency of the acoustic signal, speed of sound and signal-to-noise ratio. Most importantly, we show that the measurement error is a function of the true bearing from the array to the acoustic source.
- Under-actuated Controllability for Spacecraft RendezvousRogers, Andrew; Woolsey, Craig A.; McGwier, Robert W. (Virginia Tech, 2014-06-27)In this report, we examine the controllability of a particular form of the equations of motion for spacecraft formation flying. These equations, the Tschauner-Hempel equations, rescale the formation flying equations to a domain in which the true anomaly is the independent variable. Using this form, we are able to compute an explicit, closed-form Gramian matrix for the period of one full orbit at arbitrary eccentricity. We do this for two cases: 1) the case in which there are three inputs to the system as well as 2) the restricted case where authority only exists in the in-track and cross-track directions. This Gramian is invertible and as a result the system is controllable for both cases. Since the transformation between the time-domain, linear equations of motion and the Tschauner-Hempel equations is bijective, we conclude that the linear equations of motion are also controllable.
- Usability Evaluation in Virtual Environments: Classification and Comparison of MethodsBowman, Douglas A.; Gabbard, Joseph L.; Hix, Deborah (Department of Computer Science, Virginia Polytechnic Institute & State University, 2001)Virtual environments (VEs) are a relatively new type of human-computer interface in which users perceive and act in a three-dimensional world. The designers of such systems cannot rely solely on design guidelines for traditional two-dimensional interfaces, so usability evaluation is crucial for VEs. We present an overview of VE usability evaluation. First, we discuss some of the issues that differentiate VE usability evaluation from evaluation of traditional user interfaces such as GUIs. We also present a review of VE evaluation methods currently in use, and discuss a simple classification space for VE usability evaluation methods. This classification space provides a structured means for comparing evaluation methods according to three key characteristics: involvement of representative users, context of evaluation, and types of results produced. To illustrate these concepts, we compare two existing evaluation approaches: testbed evaluation [Bowman, Johnson, & Hodges, 1999], and sequential evaluation [Gabbard, Hix, & Swan, 1999]. We conclude by presenting novel ways to effectively link these two approaches to VE usability evaluation.
- Vehicle Dynamics in CurrentsWoolsey, Craig A. (Virginia Center for Autonomous Systems, 2011)Vehicles operating in non-uniform flow fields are subject to forces and moments that are not captured by kinematic motion models. These effects are even greater when the mass of the displaced fluid is commensurate with the mass of the vehicle, as is the case for maritime vehicles and airships. Following along the lines of a recent paper by Thomasson, this report presents a dynamic model for the motion of a rigid vehicle in a non-uniform flow. The flow field is assumed to be irrotational, comprising a steady, non-uniform component and an unsteady, uniform component. As Thomasson suggests, rotational flow effects can be incorporated by modifying the vehicle's angular rate when computing viscous forces and moments. These equations have a variety of applications for modeling, simulation, and design, a few of which are listed at the end of the report.