Distributed Sensing and Cooperating Control for Swarms of Robotic vehicles

DISTRIBUTED SENSING AND COOPERATING CONTROL FOR SWARMS OF ROBOTIC VEHICLES Key words: Distributed Sensing, Cooperative Control. ABSTRACT We discuss an approach to effectively control a large swarm of autonomous, robotic vehicles, as they per- form a search and tag operation. In particular, the robotic agents are to find the source of a chemical plume. The robotic agents work together through dis- tributed sensing and cooperative control. Distributed sensing is achieved through each agent sampling and sharing his information with others. Cooperative con- trol h accomplished by each agent u-sing its neighbors information to determine an update strategy. INTRODUCTION There is currently considerable interest in expanding the role of robotic vehicles in surveillance and inspec- tion; searching, following and t aggir-g and locating and identifying targets. In particular, researchers are beginning to focus on using small autonomous robotic vehicles for these tasks. This focus has been brought about largely because of the many recent advances in microelectronics and sensors, which include small, low power, CCD cameras; small microprocessors with ex- panded capabilities; autonomous navigation systems using GPS; and severrd types of small sensors. It seems likely that these technological advances will lead to in- expensive, easy to fabricate, autonomous vehicles out- fitted with an array of sensors. This, in turn, will allow researchers to consider teams, or even swarms, of these agents to perform a particular task. It is natural then to wonder how one might effectively control a team, or even a swarm, of robotic agents. In this paper, we discuss an approach to effectively control a large swarm of autonomous, robotic vehicles as they perform a search and tag operation. In par- ticular, the robotic agents are to find the source of a chemical plume. The robotic agents work together through distributed sensing and cooperative control. Distributed sensing is achieved through each agent sampling and sharing his information with others. Co- operative control is accomplished by each agent using its neighbors information to determine a control (or TECHNICAL DEVELOPMENT In this section we highlight the technical development of our distributed sensing and cooperative control ap- proach to effectively control a large swarm of au- tonomous, robotic vehicles. Recall that the agents are tasked with locating the chemical plume source within a chemical plume field. In our simulations, we assume that the agents are outfitted with a GPS sensor, which provides their cur- rent location, and a chemical "sniffer," which allows them to detect the strength of the chemical plume at their current location. Furthermore, we assume that the robots have onboard processing capability, and are able to communicate with one another via RF modems together with bit packing and error correction tech- niques, like those discussed by Lewis et al [4]. Thus, each agent is able to communicate and share informa- tion with all others (i.e., there is global communica- tion). In this mode, at a particular instant in time, the agents sample the chemical plume field and post this information and their current location for the oth- ers. The agents then assemble the information and de- termine a projected target of where they believe the chemical source is located. The position update for each agent is then based upon its current position and the position of the projected target

Experiments and simulations of a shocked right-cylinder perturbation

We have conducted a series of experiments using the Nova laser facility at LLNL and corresponding simulations using the two-dimensional, Arbitrary Lagrangian-Eulerian hydrodynamics code CALE. The purpose of this work was to study the shock-driven, hydrodynamic behavior of a right-cylinder perturbation. The accuracy of our simulations is examined by comparison with the experiments

Development of practical damage-mapping and inspection systems

We have developed and are continuing to refine semi-automated technology for the detection and inspection of surface and bulk defects and damage in large laser optics Different manifestations of the DAMOCLES system (Damage and Artifact Mapping Of Coherent-Laser-Exposed Substrates) provide an effective and economical means of being able to detect, map and characterize surface and bulk defects which may become precursors of massive damage in optics when subjected to high-fluence laser irradiation Subsequent morphology and evolution of damage due to laser irradiation can be tracked efficiently The strength of the Damocles system is that it allows for immediate visual observation of defects in an entire optic, which can range up to l-meter dimensions, while also being able to provide digital map and magnified images of the defects with resolutions better than 5 µm

Final Report on Rubber Foams for Run-Flat and Off-Road Tires

No abstract provided

Systems modeling and analysis of heavy ion drivers for inertial fusion energy

A computer model for systems analysis of heavy ion drivers based on induction linac technology has been used to evaluate driver designs for inertial fusion energy (IFE). Design parameters and estimated costs have been determined for drivers with various ions, different charge states, different front-end designs, with and without beam merging, and various pulse compression and acceleration schedules. We have examined the sensitivity of the results to variations in component cost assumptions, design constraints, and selected design parameter

Results of a coupled fracture-flow test at the 0.5-m scale

This report presents progress made on two experiments on 0.5-meter-scale blocks to determine thermohydromechanical (THM) behavior of fractured rock. We first present results for an experiment on sample SB3, including data for flow measurements through a horizontally oriented, artifical (saw-cut) fracture at a series of differential fluid pressures and temperatures under uniaxial stress conditions up to 14 MPa. We then present the experiment design and a progress report on the assembly of experiment SB4, flow through a vertically oriented fracture intersected by a line heat source

Quantum Monte Carlo simulations of disordered magnetic and superconducting materials

Over the last decade, Quantum Monte Carlo (QMC) calculations for tight binding Hamiltonians like the Hubbard and Anderson lattice models have made the transition from addressing abstract issues concerning the effects of electron-electron correlations on magnetic and metal-insulator transitions, to concrete contact with experiment. This paper presents results of applications of "determinant" QMC to systems with disorder such as the conductivity of thin metallic films, the behavior of the magnetic susceptibility in doped semiconductors, and Zn doped cuprate superconductors. Finally, preliminary attempts to model the Kondo volume collapse in rare earth materials are discussed

Joint inversion of geophysical data for site characterization and restoration monitoring

The purpose of this project is to develop a computer code for joint inversion of seismic and electrical data, to improve underground imaging for site characterization and remediation monitoring. The computer code developed in this project will invert geophysical data to obtain direct estimates of porosity and saturation underground, rather than inverting for seismic velocity and electrical resistivity or other geophysical properties. This is intended to be a significant improvement in the state-of-the-art of underground imaging, since interpretation of data collected at a contaminated site would become much less subjective. Potential users include DOE scientists and engineers responsible for characterizing contaminated sites and monitoring remediation of contaminated sites. In this three-year project, we use a multi-phase approach consisting of theoretical and numerical code development, laboratory investigations, testing on available laboratory and borehole geophysics data sets, and a controlled field experiment, to develop practical tools for joint electrical and seismic data interpretation

Advanced integrated modeling and measurement: The global carbon cycle

Most of the carbon dioxide added to the atmosphere by human activities comes from burning fossil fuels Only about half the CO2 we release into the atmosphere remains there, however, and the fate of the CO2 that does not remain in the atmosphere is uncertain As carbon dioxidecomes in contact with the sea surface it may be absorbed into the ocean, and as it comes in contact with the leaves of plants it may be absorbed and transformed into plant tissue, but the rates at which the sea or land plants can absorb CO2 are poorly characterized Hence, there is a great deal of uncertainty as to how much of the CO2 we release today will be found in the ocean, or in land plants, or in the atmosphere 10, 20 or 100 years from now The nanowing of these uncertainties is essential to making reliable predictions of the climate consequences of fossil fuel burning and deforestatio

Estimates of Refrigerator Loads in Public Housing Based on Metered Consumption Data

The New York Power Authority (NYPA), the New York City Housing Authority (NYCHA), and the U.S. Departments of Housing and Urban Development (HUD) and Energy (DOE) have joined in a project to replace refrigerators in New York City public housing with new, highly energy-efficient models. This project laid the ground work for the Consortium for Energy Efficiency (CEE) and DOE to enable housing authorities throughout the United States to bulk-purchase energy-efficient appliances. DOE helped develop and plan the program through the ENERGY STAR@ Partnerships program conducted by its Pacific Nofiwest National Laboratory (PNNL). PNNL was subsequently asked to conduct the savings evahations for 1996 and 1997. PNNL designed the metering protocol and occupant survey, supplied and calibrated the metering equipment, and managed and analyzed the data. The 1996 metering study of refrigerator energy usage in New York City public housing (Pratt and Miller 1997) established the need and justification for a regression-model-based approach to an energy savings estimate. The need originated in logistical difficulties associated with sampling the population and pen?orming a stratified analysis. Commonly, refrigerators[a) with high representation in the population were missed in the sampling schedule, leaving significant holes in the sample and difficulties for the stratified anrdysis. The just{jfcation was found in the fact that strata (distinct groups of identical refrigerators) were not statistically distinct in terms of their label ratio (ratio of metered consumption to label rating). This finding suggested a general regression model could be used to represent the consumption of all refrigerators in the population. In 1996 a simple two-coefficient regression model, a function of only the refrigerator label rating, was developed and used to represent the existing population of refrigerators. A key concept used in the 1997 study grew from findings in a small number of apartments metered in 1996 with a detailed protocol. Fifteen-minute time-series data of ambient and compartment temperatures and refrigerator power were analyzed and demonstrated the potential for reducing power records into three components. This motivated the development of an analysis process to divide the metered consumption into baseline load, occupant-associated load, and defrosting load. The baseline load is the consumption that would occur if the refrigerator were on but had no occupant usage load (no door-opening events) and the defrosting mechanism was disabled. The motivation behind this component reduction process was the hope that components could be more effectively modeled than the total. We reasoned that the components would lead to abetter (more general and more significant) understanding of the relationships between consumption, the characteristics of the refrigerator, and its operating environment