RCAAP Repository

The purpose of this paper is to show that ScicosLab/Scilab software can be used as an interesting and effective computational tool to analyze the automatic generation control of an electric power system for the old vertical structure as well as for the current unregulated version where the economic dispatch analysis is of fundamental importance. Firstly it is presented the software and, afterwards, the concepts and definitions of rotational movements in order to develop mathematical models for the generators equipped with steam turbines or hydraulic turbines and speed governors, and for their electrical loads. For the studies it is used a system comprised by two distinct interconnected areas where a load increase in one area is simulated without/with the tieline, ignoring, and then considering the primary and supplementary controls. Finally, it is analyzed a more realistic system with three distinct areas extracted from the Brazilian power system. The computational results show graphically the variations of the two main quantities of interest: the frequency of each area of the system and the tieline power. These quantities allow the evaluation of the system behavior after a disturbance that affects the generation-load balance. Within the above context, it is verified that the ScicosLab/Scilab computer package effectively models and simulates the load-frequency control of a power system, including the economic aspects, qualifying, therefore, as an excellent alternative to replace any similar program that requires license payment.

For the electricity be generated and distributed safely, our country has a huge and complex distribution network. Within such a network, an important component of the electrical substations. They are responsible for the control, supervision, protection and metering the flow of this energy. Due to the enormous technological advances of recent years and the great diversity of existing substation projects, the operation of which can only be performed by highly skilled professionals. Such is the demand for qualified by these professionals, their training becomes time consuming, complicated and expensive. Thus, the Virtual Reality technology proves an interesting alternative, since it enables the creation of highly realistic learning objects, with which the aspiring trader can interact without putting your life at risk and without causes financial losses. The purpose of this study is to investigate virtual reality techniques for building training environments suitable for these professionals. To perform validation of these techniques, we built a system called Virtual Reality Virtual Substation in which students can interact with a transformer power through manipulation of 3D objects or panel traditional supervisory system. Both of these views (2D and 3D) are shown simultaneously, so that the user of the system can verify how one interferes with the other. The steps performed by the trainee during the training session are stored in a System Manager database and can be retrieved by their instructor, via a 3D environment itself. After the construction of the prototype, it was presented to students of Electrical Engineering and professionals who validated his contribution as a pedagogical tool.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Cognitive radio technology has been an important area of research in telecommunications for solving the problem of spectrum scarcity. That\'s because in addition to allowing dynamic allocation of the electromagnetic spectrum, cognitive radios must be able to identify the non cognitive user\'s transmission on the channel. This operation is only possible through the continuous sensing of the electromagnetic spectrum. In this context, this paper presents a detailed study on spectrum sensing, an important stage in cognitive radio technology. For the presentation of this work, a detailed study on software dened radio (SDR) was carried out, without which it would be impossible to work with cognitive radios, once they are implemented by means of SDR technology. It was also presented the tools GNU Radio and USRP, which together form a solution of SDR, through implementation of AM receivers. The theoretical foundations of spectrum sensing and blind source separation (BSS) are presented and then is made a detailed study of the use of BSS for spectral sensing. From the study of BSS, it is possible to use new metrics for decision making about the presence or the absence of a primary user in the channel. Throughout the study, simulations and implementations were conducted on MATLAB in order to perform various situations, and, nally, it is presented outcomes and conclusions reached during the work.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

With the operation of the Pedreira Reversible Station as synchronous compensator providing reactive power to the city of São Paulo, many questions have arisen regarding the behavior of machines and the electric system in case of contingencies. Once this operation has never been performed on this system it is not possible to know what the impacts of this operation are. The ability to assess these impacts in continuous operation directs this work whose goal is to analyze the stability of the machines and the dynamics of the electrical system. Through a computer program, predetermined contingencies were simulated to represent the most common faults and events of everyday life of the electrical system. The simulations take into account the main contingencies such as loss of transmission line, load loss and others. These simulations also considered the actual settings of operation of busbars, loads and electricity generators. The main objective was to study a system composed of real electric generation, transmission and consumption of electricity, which now has connected to the network the Pedreira Reversible Station now providing reactive power to the system. The paper contains a description of all equipment present in the real system that was used to create a digital model used by the program. The construction of the model allowed the study of the electrical system through simulations that would be impossible to be made in the real electrical system.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

The research on natural interaction has been growing significantly since, with the spread of personal computers, there is an increasing demand for interfaces that maximize productivity. Among these we can highlight the interfaces Virtual Reality and Augmented Reality (KIRNER, TORI e SISCOUTO, 2006), where users can perform simple tasks such as choosing a 3D object translation, rotation and scaling in 3D object. These tasks are usually performed through devices such as the keyboard and mouse, and can, thus, a loss of immersion happen by the user in the virtual environment. Thus, investigating methodologies for natural interaction in these environments, can help increase user immersion in the virtual environment. Another issue that have been the focus of many researches are Collaborative Virtual Environments (KIRNER e TORI, 2004), where it is possible for users to communicate and share information. These users can be physically close or not. The main focus of this work is precisely the communication among remotely dispersed users. Thus, it is intended with this work, proposing a system where it is possible to manipulate 3D objects using natural gestures and share data remotely dispersed users.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The formulation of this work aims to present the suitability of Virtual Reality and Augmented Reality s methods and techniques in supporting the Measurement of Movements, which is the analysis between the observations and the physical phenomena measurement, in agreement. The use of the RA technique if gave for the fact of this to allow the virtual object insertion, as texts, images 2D, or models 3D in images of the real environment. Thus, it is proposed the development of a software in order to collect information such as speed and the acceleration by the analysis of capture images from a real environment and moving objects. A case study involving a physical experiment based on the use of an Air Track, which integrates both mechanics and kinematics principles, made possible the application of the techniques and methods formerly studied. The ARToolKit library has been used in the system s implementation. It allows the generation of Augmented Reality applications with VRML language support, which is used for modeling the virtual environment Interviews have been made by adopting a questionnaire form applied to potential users to sustain (assist) all this context. After being analysed, the system has shown itself useful in achiever the goals above.

The educational scenario has been constantly changed by the emergence of new technologies. Several researches and tools are developed in order to reframe the ways of learning and teaching inside and outside school. Information and communication technologies have caused a deep revolution in people\'s way of life in the past decades. One of the ranges that couldn\'t avoid to be affected is education and enablement (Kubota, DEMOLINER e FIGUEIREDO, 2011). The education has gotten new perspectives with the learning based on interactive technologies. Learning becomes a dynamic process and no more dependent on geographical boundaries. Hence, learning techniques arise, supported by mobile computing, which is able to take new information to the user at any time anywhere (mobile-learning or simply m-learning). This work approaches current usage of m-learning and presents a strategy of development in educational applications, using mobile devices associated with Virtual Environments and Augmented Reality. With that purpose, pattern recognition techniques related to gesture and touch are adapted and strategies of those patterns associations with library elements and between themselves, aiming to conceive virtual and augmented environments as a support for teaching. As a proof of concept, the application was implemented and evaluated, grounded in such techniques, allowing the conception of Physics experiments (Classic Mechanics).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The purpose of this thesis is the acting study and efficiency of the linear induction motor, applied as driver of the discharge dam in dryers of cereals, in substitution to the Conventional System used previously, composed by a system electric pneumatic, group compressor, pneumatic piston and accessories. The search of this purpose based on the looking for of solutions to reduce the high index of defects of the Conventional System, and that the Proposed System had simple and robust constitution, demanding little maintenance for having few potential points of defects, and at the same time to present technological innovation, productive efficiency and low consumption of energy. For this it was projected and built a denominated equipment of simulator of the dam of discharge of dryer of cereals, with flow scale ten times minor than the field system application, and in this simulator the linear induction motor was adapted [Thé Pontes, 2003], where the tests of operation of the simulator were made for load conditions, measurements of force and consumption of energy. The obtained results are very close to the expected and they assist perfectly to the objectives of this work.

The IEEE 802.16e standard is an important technology for wireless broadband communication, which allows high transfer rates, long reach and mobility. One of its main features is the quality of service (QoS) provision for applications. This is achieved through a connection admission control (CAC) scheme, which determines whether or not a connection can be established according to the network resources availability, a traffic policing scheme and also a packet scheduling scheme, that defines which service class should be served with the higher priority, based on predetermined criteria. As the standard does not define the policies to implement these mechanisms, this work proposes a CAC mechanism for IEEE 802.16e standard, based on dynamic bandwidth reservation. These reserves are obtained by segmenting the amount of the channel s bandwidth by thresholds, which are dynamically adjusted according to the admissions of handoff and new connections. Experiments were performed through modeling and simulation, demonstrating that the proposed mechanism can avoid the waste of network resources, increases its efficiency and provide QoS, in terms of bandwidth, for applications.

The increased demand in transport and energy industry has led to the search for low cost maintenance techniques. The technique most commonly used is the electric-arc welding. However, it presents a higher cost for use in special environments, and a potential risk to the microstructure of the repaired material. As an alternative, the Friction Repair technique was developed, in which a hole is drilled at the damage area, and filled with a consumable rod submitted to a rotation speed and axial force. Looking forward to applying this technology, the company Petrobras signed an agreement with the Federal University of Uberlandia - Brazil, and a Friction Hydro Pillar Processing Machine was developed. It was used to optimize the parameters and geometries for the new technique. Later, studies for field application began towards designing a portable friction welding head, which is the mechanical part that applies axial load and rotation to the consumable rod. This study aimed to design a new instrumentation and control system to this portable equipment, allowing the performance of friction repais through an automated equipment. Transducers were used for reading the parameters during the tests, and electronic devices were developed for signal conditioning. Additionally, it was adjusted the PID control loops, and a software was developed for data management and monitoring tool during the entire process. Tests were conducted of the various devices used for this project, resulting in the validation of the developed system.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior