The concept of Cognitive radio enables the unlicensed users to share the spectrum with licensed users, on the condition that the licensed users have preemptive priority. The use of the channel by unlicensed users should not result in more than acceptable interference level to the licensed users, if interference occurs. The sense and react strategy by unlicensed users sometimes does not lead to acceptable level of interference while maintaining an acceptable data transfer rate for the unlicensed users. Proactive channel access has been proposed for the purpose of reducing the interference to primary users and to reduce the idle channel search delay for the secondary users. There are many methods used in the literature to model the channel state fluctuations. Based on these models the future channel states are predicted. In this thesis we introduce a predictive channel usage scheme which is capable of reducing the interference caused by the unlicensed users. Furthermore our scheme is capable of increasing the data rates the unlicensed users experience through the reduction of the idle channel identification delay. In our scheme no assumptions are made about the distribution of licensed user channel usage. We learn the traffic characteristics of the channels using a learning scheme called Probabilistic Suffix Tree algorithm.

The concept of Cognitive radio enables the unlicensed users to share the spectrum with licensed users, on the condition that the licensed users have preemptive priority. The use of the channel by unlicensed users should not result in more than acceptable interference level to the licensed users, if interference occurs. The sense and react strategy by unlicensed users sometimes does not lead to acceptable level of interference while maintaining an acceptable data transfer rate for the unlicensed users. Proactive channel access has been proposed for the purpose of reducing the interference to primary users and to reduce the idle channel search delay for the secondary users. There are many methods used in the literature to model the channel state fluctuations. Based on these models the future channel states are predicted. In this thesis we introduce a predictive channel usage scheme which is capable of reducing the interference caused by the unlicensed users. Furthermore our scheme is capable of increasing the data rates the unlicensed users experience through the reduction of the idle channel identification delay. In our scheme no assumptions are made about the distribution of licensed user channel usage. We learn the traffic characteristics of the channels using a learning scheme called Probabilistic Suffix Tree algorithm.

The current air traffic management system has primarily evolved via incremental changes around historic control, navigation, and surveillance technologies. As a result, the system as a whole is not capable of handling air traffic capacities well beyond current levels, despite recent developments, such as ADS-B, that could potentially enable new concepts of operation. Methods of analyzing air traffic for safety and performance have also evolved around current-day operating constructs. Thus, attempts to examine future systems tend to use different analysis methods developed for each. Most notably, questions of 'locus of control' - whether the control should be centralized or de-centralized and distributed - have no common framework by which to judge relative costs and benefits. For instance, a completely centralized control paradigm is commonly asserted to provide an airspace-wide optimal traffic management solution due to a more complete picture of the state of the airspace, whereas a completely decentralized control paradigm is commonly asserted to provide a more user-specific optimal traffic management solution, to distribute the traffic management workload, and potentially be more robust. Given the disparate nature of these assertions and the different types of evaluations commonly used with each, some shared framework must be established to allow comparisons between very different control paradigms. The objective of this thesis was to construct a formal framework to examine the relative costs and benefits of shifting the locus of control in a novel air traffic management environment. This framework provides useful definitions and quantitative measures of flexibility and robustness with respect to various control paradigms ranging between, and including, completely centralized and completely decentralized concepts of operation. Multi-agent dynamic analysis and simulation was used to analyze the range of dynamics found in the different control paradigms. In addition, futuristic air traffic management concepts were developed in sufficient detail to demonstrate the framework. In other words, the objectives were met because the framework was demonstrated to have the ability to identify (or dispel) hypotheses about the relative costs and benefits of locus of control.

The main objective of this thesis was to develop appropriate system protection schemes against two important causes of failure in power systems, namely, long-term voltage instability and cascade tripping of overloaded transmission lines, mainly due to overloading. To this purpose a distributed undervoltage load shedding scheme against voltage instability, and a centralized protection meant to alleviate line overload are proposed. The former, through the chosen system protection scheme characteristics, has the ability to adjust its actions to the disturbance location and severity. This behavior is achieved without resorting to a dedicated communication network. The distributed controllers do not exchange information, but are rather informed of their respective actions through voltage measurements. Neither do the controllers require a model of the system. This and the absence of communication makes the protection scheme simple and reliable. The other protection scheme, inspired of model predictive control, is aimed at bringing the currents in the overloaded lines below their limits in the time interval left by protections, while accounting for constraints on control changes. Its closed-loop nature allows to compensate for model uncertainties and measurement noise. In order to tune the proposed system protection schemes parameters and validate their performance it was preferred to detect plausible cascading event scenarios. To this purpose, an algorithm meant to identify such complex sequences has been developed. It encompasses hidden failures and the resulting system response. The tests performed on small systems as well as on a real-life one confirm not only that proposed protection schemes appropriately deal with the problems for which they were designed, but also that they cooperate satisfactorily for combined voltage and thermal problems that are beyond their individual capabilities.

&ldquo / Numerically Controlled&rdquo / (NC) machine tools, which are automatically operated by encoded (digital) commands, are capable of machining components with quality and quantity. Manufacturing industry heavily depends on these machines. Many different control architectures have been adapted in today&rsquo / s CNC technology. Centralized control system is quite popular in industry due to its ease of implementation. If the number of controlled axes on a CNC machine tool (&gt / 3), increases so does the computational burden on the central processors. Hence, more powerful processors are needed. An alternative architecture, which is not commonly used in CNC technology, is the decentralized (distributed) control. In this topology, the tasks handled by the distributed controllers that are interconnected to each other by a communication network. As the need arises, a new controller can be added easily to the network without augmenting the physical configuration. Despite its attractive features, this architecture has not been fully embraced by the CNC industry. Synchronization among the axes in the coordinated motion is proven to be quite challenging. In this thesis, alternative distributed controller architecture was proposed for CNC machine tools. It was implemented on a 3-axis CNC milling machine. Open-loop control performance was investigated under various conditions. Different communication protocols along with different physical communication interfaces and a number of controller hardware were devised. An industry-standard network (RS-485) was set up by interconnecting these distributed controllers. Different data transmission protocols were devised in order to establish appropriate communication methods. Also, computer software (a.k.a. graphical user interface), which can coordinate the interconnected controllers, interpret NC part programs and generate reference position data for each axis, was designed within the scope of this thesis.

ABB s r.o. is one of the most important companies that are concerned with setting of trends in electro-energetic field. One of these trends is digitalization of medium voltage substations that leads to simplified of internal connection and easier connection of substation to the control system. This thesis deals possibilities of connection of communication, methods of controlling logical operations by centralized or distributed system and compares potential of these systems.

Solar and wind generation are one of the most rapidly growing renewable energy sources, and is regarded as an appealing alternative to conventional power generated from fossil fuel. This is leading to significant levels of distributed renewable generation being installed on distribution circuits. Although renewable generation brings many advantages, circuit problems are created due to its intermittency, and overcoming these problems is a key challenge to achieving high penetration. It is necessary for utilities to understand the impacts of Photovoltaic (PV) generation on distribution circuits and operations. An impact study is intended to quantify the extent of the issues, discover any problems, and investigate alternative solutions. In this manner, system wide and local impact study are proposed in the dissertation. 1) System wide impact study This study considers system effects due to the addition of Plug-in Hybrid Vehicles (PHEV) and Distributed Energy Resource (DER) generation. The DER and PHEV are considered with energy storage technology applied to the residential distribution system load. Two future year scenarios are considered, 2020 and 2030. The models used are of real distribution circuits located near Detroit, Michigan, and every customer load on the circuit and type of customer are modeled. Monte Carlo simulations are used to randomly select customers that receive PHEV, DER, and/or storage systems. The Monte Carlo simulations provide not only the expected average result, but also its uncertainty. 2) Local impact study Analysis of high PV penetration in distribution circuits using both steady-state and quasi steady-state impact studies are presented. The steady-state analysis evaluates impacts on the distribution circuit by comparing conditions before and after extreme changes in PV generation at three extreme circuit conditions, maximum load, maximum PV generation, and when the difference between the PV generation and the circuit load is a maximum. The quasi steady-state study consists of a series of steady-state impact studies performed at evenly spaced time points for evaluating the spectrum of impacts between the extreme impacts. Results addressing the impacts of cloud cover and various power factor control strategies are presented. PV penetration levels are limited and depend upon PV generation control strategies and the circuit design and loading. There are tradeoffs in PV generation control concerning circuit voltage variations, circuit losses, and the motion of automated utility control devices. The steady state and quasi steady-state impact studies provide information that is helpful in evaluating the effect of PV generation on distribution circuits, including circuit problems that result from the PV generation. In order to fully benefit from wind power, accurate wind power forecasting is an essential tool in addressing this challenge. This has motivated researchers to develop better forecast of the wind resources and the resulting power. As a solution for wind generation, frequency domain approach is proposed to characterize and analyze wind speed patterns in the dissertation. 3) Frequency Domain Approach This study introduces the frequency domain approach to characterize and analyze wind speed patterns. It first presents the technique of and the prerequisite conditions for the frequency domain approach. Three years of wind speed data at 10 different locations have been used. This chapter demonstrates that wind speed patterns during different times and at different locations can be well characterized by using the frequency domain approach with its compact and structured format. We also perform analysis using the characterized dataset. It affirms that the frequency domain approach is a useful indicator for understanding the characteristics of wind speed patterns and can express the information with superior accuracy. Among the various technical challenges under high PV penetration, voltage rise problems caused by reverse power flows are one of the foremost concerns. The voltage rises due to the PV generation. Furthermore, the need to limit the voltage rise problem limits PV generators from injecting more active power into the distribution network. This can be one of the obstacles to high penetration of PVs into circuits. As a solution for solar generation, coordinated control of automated devices and PV is proposed in the dissertation. 4) Coordinated Automated Device and PV Control A coordinating, model-centric control strategy for mitigating voltage rise problems due to PV penetration into power distribution circuits is presented. The coordinating control objective is to maintain an optimum circuit voltage distribution and voltage schedule, where the optimum circuit operation is determined without PV generation on the circuit. In determining the optimum circuit voltage distribution and voltage schedule, the control strategy schedules utility controls, such as switched capacitor banks and voltage regulators, separate from PV inverter controls. Optimization addresses minimizing circuit losses and motion of utility controls. The coordinating control action provides control setpoints to the PV inverters that are a function of the circuit loading or time-of-day and also the location of the PV inverter. Three PV penetration scenarios are considered, 10%, 20%, and 30%. Baselines with and without coordinating controls for circuit performance without PV generation are established, and these baselines are compared against the three PV penetration scenarios with and without coordinating control. Simulation results are compared and differences in voltage variations and circuit losses are considered along with differences in utility control motion. Results show that the coordinating control can solve the voltage rise problem while minimizing circuit losses and reducing utility control motion. The coordinating control will work with existing PV inverter controls that accept control setpoints without having to modify the inverter controls. 5) Coordinated Local and Centralized PV Control Existing distribution systems and their associated controls have been around for decades. Most distribution circuits have capacity to accommodate some level of PV generation, but the question is how much can they handle without creating problems. It proposes a Configurable, Hierarchical, Model-based, Scheduling Control (CHMSC) of automated utility control devices and photovoltaic (PV) generators. In the study here the automated control devices are assumed to be owned by the utility and the PV generators and PV generator controls by another party. The CHMSC, which exists in a hierarchical control architecture that is failure tolerant, strives to maintain the voltage level that existed before introducing the PV into the circuit while minimizing the circuit loss and reducing the motion of the automated control devices. This is accomplished using prioritized objectives. The CHMSC sends control signals to the local controllers of the automated control devices and PV controllers. To evaluate the performance of the CHMSC, increasing PV levels of adoption are analyzed in a model of an actual circuit that has significant existing PV penetration and automated voltage control devices. The CHMSC control performance is compared with that of existing, local control. Simulation results presented demonstrate that the CHMSC algorithm results in better voltage control, lower losses, and reduced automated control device motion, especially as the penetration level of PV increases. / Ph. D.

This study takes advantage of wide area measurements to propose a centralized nonlinear controller that acts on power system stabilizers, to cooperatively increase the damping of problematic small signal oscillations all over the system. The structure based on decision trees results in a simple, efficient, and dependable methodology that imposes much less computational burden than other nonlinear design approaches, making it a promising candidate for actual implementation by utilities and system operators. Details are given to utilize existing stabilizers while causing minimum changes to the equipment, and warranting improvement or at least no detriment of current system behavior. This enables power system stabilizers to overcome their inherent limitation to act only on the basis of local measurements to damp a single target frequency. This study demonstrates the implications of this new input on mathematical models, and the control functionality that is made available by its incorporation to conventional stabilizers. In preparation of the case of study, a heuristic dynamic reduction methodology is introduced that preserves a physical equivalent model, and that can be interpreted by any commercial software package. The steps of this method are general, versatile, and of easy adaptation to any particular power system model, with the aggregated value of producing a physical model as final result, that makes the approach appealing for industry. The accuracy of the resulting reduced network has been demonstrated with the model of the Central American System. / Ph. D.

Approved for public release; distribution in unlimited. / Military leaders and scholars alike debate the existence of a revolution in military affairs (RMA) based on information technology. This thesis will show that the Information RMA not only exists, but will also reshape how we plan, operate, educate, organize, train, and equip forces for the 21st century. This thesis introduces the Communication Technology (CommTech) Model to explain how communication technologies affect organizations, leadership styles, and decision-making processes. Due to the growth in networking enterprises, leaders will have to relinquish their tight, centralized control over subordinates. Instead, they will have to perfect their use of softer power skills such as influence and trust as they embrace decentralized decision-making. Network Centric Warfare, Self-Synchronization, and Network Enabled Operations are concepts that provide the framework for integrating information technology into the battlespace. The debate that drives centralized versus decentralized control in network operations is analyzed with respect to the CommTech Model. A new term called Operational Trust is introduced and developed, identifying ways to make it easier to build trust among network entities. Finally, the thesis focuses on what leaders need to do to shape network culture for effective operations. / Major, United States Air Force

<div>Multi-robot systems have demonstrated strong capability in handling environmental operations. In this study, We examine how a team of robots can be utilized in covering and removing spill patches in a dynamic environment by executing three consecutive stages: deployment, coverage, and rendezvous. </div><div> </div><div>For the deployment problem, we aim for robot allocation based on the discreteness of the patches that need to be covered. With the deep neural network (DNN) based spill detector and remote sensing facilities such as drones with vision sensors and satellites, we are able to obtain the spill distribution in the workspace. Then, we formulate the allocation problem in a general optimization form and provide solutions using an integer linear programming (ILP) solver under several realistic constraints. After the allocation process is completed and the robot team is divided according to the number of spills, we deploy robots to their computed optimal goal positions. In the robot deployment part, control laws based on artificial potential field (APF) method are proposed and practiced on robots with a common unicycle model. </div><div> </div><div>For the coverage control problem, we show two strategies that are tailored for a wirelessly networked robot team. We propose strategies for coverage with and without path planning, depending on the availability of global information. Specifically, in terms of coverage with path planning, we partition the workspace from the aerial image into pieces and let each robot take care of one of the pieces. However, path-planning-based coverage relies on GPS signals or other external positioning systems, which are not applicable for indoor or GPS-denied circumstances. Therefore, we propose an asymptotic boundary shrink control that enables a collective coverage operation with the robot team. Such a strategy does not require a planned path, and because of its distributedness, it shows many advantages, including system scalability, dynamic spill adaptability, and collision avoidance. In case of a large-scale patch that poses challenges to robot connectivity maintenance during the operation, we propose a pivot-robot coverage strategy by mean of an a priori geometric tessellation (GT). In the pivot-robot-based coverage strategy, a team of robots is sent to perform complete coverage to every packing area of GT in sequence. Ultimately, the entire spill in the workspace can be covered and removed.</div><div> </div><div>For the rendezvous problem, we investigate the use of graph theory and propose control strategies based on network topology to motivate robots to meet at a designated or the optimal location. The rendezvous control strategies show a strong robustness to some common failures, such as mobility failure and communication failure. To expedite the rendezvous process and enable herding control in a distributed way, we propose a multi-robot multi-point rendezvous control strategy. </div><div> </div><div>To verify the validity of the proposed strategies, we carry out simulations in the Robotarium MATLAB platform, which is an open source swarm robotics experiment testbed, and conduct real experiments involving multiple mobile robots.</div>