Jerry C. Hamann

Distributed, Physics-Based Control of Swarms of Vehicles

We introduce a framework, called “physicomimetics,” that provides distributed control of large collections of mobile physical agents in sensor networks. The agents sense and react to virtual forces, which are motivated by natural physics laws. Thus, physicomimetics is founded upon solid scientific principles. Furthermore, this framework provides an effective basis for self-organization, fault-tolerance, and self-repair. Three primary factors distinguish our framework from others that are related: an emphasis on minimality (e.g., cost effectiveness of large numbers of agents implies a need for expendable platforms with few sensors), ease of implementation, and run-time efficiency. Examples are shown of how this framework has been applied to construct various regular geometric lattice configurations (distributed sensing grids), as well as dynamic behavior for perimeter defense and surveillance. Analyses are provided that facilitate system understanding and predictability, including both qualitative and quantitative analyses of potential energy and a system phase transition. Physicomimetics has been implemented both in simulation and on a team of seven mobile robots. Specifics of the robotic embodiment are presented in the paper.

Where are you

The ability of robots to quickly and accurately localize their neighbors is extremely important in swarm robotics. Prior approaches generally rely either on global information provided by GPS, beacons, and landmarks, or complex local information provided by vision systems. In this paper we provide a new technique, based on trilateration. This system is fully distributed, inexpensive, scalable, and robust. In addition, the system provides a unified framework that merges localization with information exchange between robots. The usefulness of this framework is illustrated on a number of applications.

Transformations and destruction of nitrogen oxides: No, NO2 and N2O: in a pulsed corona discharge reactor

Abstract There has been an increasing recent research interest in the removal of NO x from combustion gases using electrical discharges, especially pulsed corona discharge reactors. The major issues in development of this technology are (a) the energy consumption required to achieve the desired pollutant reduction; and (b) the formation of undesirable byproducts. In this study, the transformations and destruction of nitrogen oxides—NO, NO 2 and N 2 O—were investigated in a pulsed corona discharge reactor. Gas mixtures—NO in N 2 , N 2 O in N 2 , NO 2 in N 2 and NO–N 2 O–NO 2 in N 2 —were allowed to flow through the reactor with initial concentrations, flow rates and energy input as operating variables. The reactor effluent gas stream was analyzed for N 2 O, NO, NO 2 , by means of an FTIR spectrometer. In some experiments, oxygen was measured using a gas chromatograph. Reaction mechanisms were proposed for the transformations and destruction of the different nitrogen oxides within a unified model structure. The corresponding reaction rates were integrated into a simple reactor model for the pulsed corona discharge reactor. The reactor model brings forth the coupling between reaction rates, electrical discharge parameters, and fluid flow within the reactor. It was recognized that the electron-impact dissociation of the background gas N 2 leads to both ionic and radical product species. In fact, ionic reactions were found responsible for N 2 O destruction. Radical reactions were dominant in the transformation and destruction of NO and NO 2 . However, decomposition of N 2 + ions also leads to indirect production of N radicals; this appears to be a less-power intensive route for NO destruction though longer residence times may be necessary. In addition, the decomposition of N 2 + ions limits the N 2 O destruction that can be achieved. Comparison with our experimental data, as well as data in the literature, was very encouraging.

Fibre Channel Switch Modeling at Fibre Channel-2 Level for Large Fabric Storage Area Network Simulations using OMNeT++: Preliminary Results

Black hole attacks are a serious threat to communication in tactical MANETs. In this work we present TOGBAD a new centralised approach, using topology graphs to identify nodes attempting to create a black hole. We use well-established techniques to gain knowledge about the network topology and use this knowledge to perform plausibility checks of the routing information propagated by the nodes in the network. We consider a node generating fake routing information as malicious. Therefore, we trigger an alarm if the plausibility check fails. Furthermore, we present promising first simulation results. With our new approach, it is possible to already detect the attempt to create a black hole before the actual impact occurs.Abstract—Typically, in the current enterprise data centers dedicated fabrics or networks are implemented to meet their LAN, Inter-Processor communication and storage traffic requirements. The storage traffic requirements of a group of servers are met through multiple storage area networks based on fibre channel, which has become the standard connection type. Typically, this fibre channel storage area networks are small (maximum of 32 switches/directors in a single fabric) and do not experience any scaling, stability and other performance issues. The advent of I/O consolidation in enterprise data centers for multiple traffic types to converge on to a single fabric or network (typically Ethernet platform) to reduce hardware, energy and management costs has also the potential to allow implementation of large storage area networks based on the fibre channel standards. Large storage area networks are being planned with more than two hundred switches/directors in a single fabric or network in addition to servers and storages connected to the fabric on Ethernet platforms. Even though these large storage area networks are envisioned to operate on Ethernet platform, they still have to satisfy the stringent operating and performance requirement set forth by the fibre channel standards. The two important issues of concern with large storage area networks are scaling and stability. The scaling and stability issues are dependent on the interactions and performance capabilities of various fabric servers located on each switch/director in the fabric in order to provide fabric services. In order to determine the extent of scaling and stability issues of a large fabric first the detailed models of the switch/director addressing the operations of the individual fabric servers are required. Next, the interactions of the switches/directors using the detailed models are to be simulated to study the scaling and stability issues. In this paper, the detailed modeling of the fibre channel switch and the fabric servers using the OMNeT++ discrete event simulator is presented first. Detailed models are developed addressing the behavior of the switch at the level-2 of the fibre channel protocol since this layer addresses the requirements and operations of various mandatory fabric services like fabric build, directory, login, nameserver, management, etc. Next, using the OMNET++ discrete event simulator large fabrics are simulated. The results from the simulation are compared against the test bed traffic and the accuracy is demonstrated. Also, results and analysis of multiple simulations with increasing fabric size are presented.

Cooperative education as a means to enhance self-efficacy among sophomores (with particular attention to women) in undergraduate engineering

Northeastern University and the University of Wyoming are investigating whether the participation of sophomores (with particular attention to women) in formal undergraduate engineering programs that provide work experiences while enrolled (e.g., cooperative education and internships) is related to enhanced self-efficacy. While self-esteem is a global concept and self-efficacy refers to confidence about a particular content area or set of tasks, general self-esteem tends to be related to an individuals feelings of self-efficacy. Research suggests that decreased self-esteem and self-efficacy of women in engineering majors are significant obstacles to persistence. Indeed, consistent findings reported through the assessing women in engineering project have reported that the persistence of women in engineering is highly related to efficacy. Thus, this study was designed to add to the body of literature on the retention of women in undergraduate engineering. The purpose of this study is to isolate those factors that contribute most to the development of three positive self- efficacy dimensions thought to be most relevant to the retention of sophomores (especially women) in undergraduate engineering: work, academic, and career It examines, in particular, if cooperative education alone enhances efficacy (while controlling for pre-existing conditions among students enrolling in a cooperative education school as well as controlling for alternative supports for students to assist them during their undergraduate experience). One of the schools participating in the study, Northeastern, requires cooperative (co-op) education whereas the University of Wyoming does not.

A physicomimetics control framework for swarms of Autonomous Surface Vehicles

Teams of autonomous cooperating vehicles are well-suited for meeting the challenges associated with mobile marine sensor networks. Swarms built using a physicomimetics approach exhibit predictable behavior - an important benefit for extended duration deployments of autonomous ocean platforms. By using a decentralized control framework, we minimize energy consumption via short-range communication and self-contained on-board data processing, all without a specified leader. We introduce the task of autonomous surface vehicle (ASV) navigation inside a bioluminescent plume to motivate future study of how the agility and scalability of our physics-based solution can benefit a mobile distributed sensor network.

Reinforcing the understanding of signal processing concepts using audio exercises

In the near future, multimedia techniques will be used more extensively in signal processing education because the technology is available and the benefits to student learning and information retention are high. Using a variety of teaching techniques helps a wider range of students, who have different learning styles, and enhances student skills in their weaker areas. This paper describes a number of audio signal processing homework exercises used to reinforce concepts of signal processing. These exercises include some fundamental concepts of DSP (quantization, aliasing, Fourier analysis, and filtering) and more advanced areas (sampling rate conversion, LCMV filtering, and adaptive filtering). All these exercises use the signal processing and audio capabilities of MATLAB. A Web page for these homework exercises is being developed.

Using Monte Carlo simulations to introduce tolerance design to undergraduates

The effect of parameter variations on engineering systems is often neglected in undergraduate electrical engineering education. This paper proposes using Monte Carlo simulation to introduce students to tolerance design in the required electronics course where students perform designs using real electronic components. Monte Carlo simulation requires very little statistical background for the student and many software packages have built-in random number generators or even Monte Carlo simulation options, As a result, tolerance design is easily introduced to students in a short time frame. This paper discusses methods of introducing Monte Carlo simulations to the students in less than one hour of lecture. Example laboratory exercises and homework problems are described.

Optimal fault tolerant control of flexure jointed hexapods for applications requiring less than six degrees of freedom

When less than 6 degrees-of-freedom (DOF) are required (in precision pointing tasks, for example), the kinematic redundancy of a Stewart platform (or hexapod) makes it possible to implement fault tolerant algorithms. When one or several of the platform legs (struts) fail, methods are presented in this paper for finding a new, reconfigured control to maintain performance.

Integrated design laboratory

Workbenches in traditional student electronics laboratories have supported courses primarily in areas of circuits and electronics. Unfortunately, it has been difficult to design meaningful hands-on exercises for other courses such as signals and systems, communications, control, and digital signal processing using typical workbench setups. This paper describes the development of a new workbench design that effectively supports a wide range of courses in electrical and computer engineering. Each bench is fully integrated through a computer interfaced to IEEE-488-based test and measurement equipment. Additionally, each includes a high-speed data acquisition systems as well as an outboard DSP hardware system. This paper describes the test bench setup and illustrates its use by examples from several different courses.