A hybrid current controller for linear reciprocating vapor compressors

Direct-drive linear reciprocating compressors offer numerous advantages over conventional counterparts which are usually driven by a rotary induction motor via crank shaft However, to ensure efficient and reliable operation under all conditions, it is essential that the motor current of the linear compressor follows a sinusoidal command profile with a frequency which matches the system resonant frequency. This paper describes a hybrid current controller for the linear compressors. It comprises a conventional proportional-integral (PI) controller, and a B-spline neural network compensator which is trained on-line and in real-time in order to minimize the current tracking error under all conditions with uncertain disturbances. It has been shown that the hybrid current controller has a superior steady-state and transient performance over the conventional carrier based PI controller. The performance of the proposed hybrid controller has been demonstrated by extensive simulations and experiments. It has also been shown that the linear compressor operates stably under the current feedback control and the piston stroke can be adjusted by varying the amplitude of the current command. © 2007 IEEE.

Single-phase active rectifier selection for fault tolerant machine

A fault tolerant, 5-phase PM generator has been developed for use on the low pressure (LP) shaft of an aircraft gas turbine engine. The machine operates at variable speed and therefore has a variable voltage, variable frequency electrical output (VVVF). The generator is to be used to provide a 350V DC bus for distribution throughout the aircraft, and a study has been carried out that identifies the most suitable AC-DC converter topology for this machine in terms of losses, electrical component ratings, filtering requirements and circuit complexity.

Permanent magnet synchronous generator based wind power generation system fault protection schemes

The PMSG-based wind power generation system protection is presented in this paper. For large-scale systems, a voltagesource converter rectifier is included. Protection circuits for this topology are studied with simulation results for cable permanent fault conditions. These electrical protection methods are all in terms of dumping redundant energy resulting from disrupted path of power delivery. Pitch control of large-scale wind turbines are considered for effectively reducing rotor shaft overspeed. Detailed analysis and calculation of damping power and resistances are presented. Simulation results including fault overcurrent, DC-link overvoltage and wind turbine overspeed are shown to illustrate the system responses under different protection schemes to compare their application and effectiveness.

Prospecção tecnológica para geração de energia eólica

The acceleration of technological change and the process of globalization has intensified competition and the need for new products (goods and services), resulting in growing concern for organizations in the development of technological, economic and social advances. This work presents an overview of the development of wind energy-related technologies and design trends. To conduct this research, it is (i) a literature review on technological innovation, technological forecasting methods and fundamentals of wind power; (ii) the analysis of patents, with the current technology landscape studied by means of finding information in patent databases; and (iii) the preparation of the map of technological development and construction of wind turbines of the future trend information from the literature and news from the sector studied. Step (ii) allowed the study of 25 644 patents between the years 2003-2012, in which the US and China lead the ranking of depositors and the American company General Electric and the Japanese Mitsubishi stand as the largest holder of wind technology. Step (iii) analyzed and identified that most of the innovations presented in the technological evolution of wind power are incremental product innovations to market. The proposed future trends shows that the future wind turbines tend to have a horizontal synchronous shaft, which with the highest diameter of 194m and 164m rotor nacelle top, the top having 7,5MW generation. The materials used for the blades are new materials with characteristics of low density and high strength. The towers are trend with hybrid materials, uniting the steel to the concrete. This work tries to cover the existing gap in the gym on the use of technological forecasting techniques for the wind energy industry, through the recognition that utilize the patent analysis, analysis of scientific articles and stories of the area, provide knowledge about the industry and influencing the quality of investment decisions in R & D and hence improves the efficiency and effectiveness of wind power generation

Three-dimensional tomographic reconstruction of an exceptionally well preserved ichnological assemblage from the Stainmore Foundation, Carboniferous, UK

This Ph.D. thesis addresses current issues with ichnotaxonomic practice, and characterizes an exceptionally well preserved ichnological assemblage from the Carboniferous Stainmore Formation, Northumberland, United Kingdom. Samples were collected from closely localized float representative of various units throughout the succession, which was deposited in a storm-dominated marine shoreface. Three dominant ichnotaxa were selected for three-dimensional morphological analysis due to their complicated morphology and/or unclear taxonomic status: 1) Dactyloidites jordii isp. nov.; 2) Beaconites capronus, and; 3) Neoeione moniliformis comb. nov. Using serial grinding and photography, these ichnotaxa were ground and modelled in true colour. High-resolution models of three taxa produced in this study are the basis of the first complete three-dimensional consideration of the traces, and forms the basis for refined palaeobiological and ethological analysis of these taxa. Dactyloidites jordii isp. nov. is a stellate to palmate burrow composed of numerous long, narrow rays that exhibit three orders of branching arranged into tiered galleries radiating from a central shaft. It is considered to be the feeding structure produced by a vermiform organism. Beaconites capronus is a winding trace with distinctly chevron-shaped, meniscate backfill demonstrated herein to backfill the vertical shafts associated with its burrows in a comparable fashion to the horizontal portion of the burrow. This lack of a surface connection would result in the trace making organism being exposed to low-oxygen porewater. Coping with this porewater dysoxia could be approached by burrowing organisms in a number of ways: 1) revisiting the sediment-water interface; 2) creating periodic shafts; or 3) employing anaerobic metabolism. Neoeione moniliformis was originally introduced as Eione moniliformis, however, the genus Eione Tate, 1859 is a junior homonym of Eione Rafinesque, 1814. This led to the transfer of Eione moniliformis to Parataenidium. Through careful examination and three-dimensional characterization of topotypes, the transfer to Parataenidium moniliformis is demonstrated herein to be problematic, as Parataenidium refers to primarily horizontal burrows with two distinct layers and Eione moniliformis is composed of one distinct level. As such, the new ichnogenus Neoeione is created to accommodate Neoeione moniliformis.

Do acesso clássico à comercialização: especificidades do mercado imobiliário informal na área especial de interesse social de Mãe Luiza, Natal/ RN.

This study presents research regarding affordable housing and their effects on the spatial reconfiguration of Natal/ RN, aiming to identify the specificities of the informality of urban land. This study aims to understand how informal housing market operates housing provision for the population located in popular informal settlements, through buying and selling market and rental market of residential properties irregular / illegal. This understanding will be through the neighborhood of Mãe Luisa, Special Area of Social Interest (SASI), located between neighborhoods with a population of high purchasing power and inserted into the tourist shaft of seaside of town. The characterization of informal housing market in Mãe Luiza, from buyers, sellers and renters, will help to understand how these informal transactions operate on SASI and housing provision for public policy development and implementation of housing programs and land regularization for low-income population, adequate to dynamic and reality of housing of informal areas

Electronic Redesign of an Industrial Lift

This project, realized at the company ABER Ltd, describes the process followed for the developing of an electronic control system for a hydraulic elevator. The previous control system was based on relay logic, and the company wanted to change it to a microcontroller based technology. To do so, different approaches were studied and finally the selected technology for the development was the Raspberry Pi. After, the software needed for all the elevator types was developed, and the interface hardware was selected. In the end, several test were made to adjust the software and the hardware and to prove the good operation of the system.

Tire inspection spreading machine

The aim of the project was to design in Solidworks and improve an existing Tire inspection machine. The project was developed in Gislotica - Mechanical Solutions, guided by ing. Rui Manuel Fazenda Silva who is a professor in ISEP. The designed device relates to the inspection of automobile tires for holes and weak places caused by punctures and usage. Such inspection includes careful examination of the inside surface of the tire which is difficult because of its cylindrical shape, stiff and resistant nature of the material out of which the tire is made. The whole idea is to provide a machine by which the walls of the tire may be spread and hold apart, presenting the inner surface for the worker to control. The device must also perform rotational and vertical movement of the tire. It is meant to provide inspection in hich there is no need for the controller to use force. It makes his work easier and more efficient.

Análise e modelagem do escoamento transitório de fluidos de perfuração

Drilling fluids present a thixotropic behavior and they usually gel when at rest. The sol-gel transition is fundamental to prevent the deposit of rock fragments, generated by drilling the well, over the drill bit during eventual stops. Under those conditions, high pressures are then required in order to break-up the gel when circulation is resumed. Moreover, very high pressures can damage the rock formation at the bottom of the well. Thus, a better understanding of thixotropy and the behavior of thixotropic materials becomes increasingly important for process control. The mechanisms that control thixotropy are not yet well defined and modeling is still a challenge. The objective of this work is to develop a mathematical model to study the pressure transmission in drilling fluids. This work presents a review of thixotropy and of different mathematical models found in the literature that are used to predict such characteristic. It also shows a review of transient flows of compressible fluids. The problem is modeled as the flow between the drillpipe and the annular region (space between the wall and the external part of the drillpipe). The equations that describe the problem (mass conservation, momentum balance, constitutive and state) are then discretized and numerically solved by using a computational algorithm in Fortran. The model is validated with experimental and numerical data obtained from the literature. Comparisons between experimental data obtained from Petrobras and calculated by three viscoplastic and one pseudoplastic models are conducted. The viscoplastic fluids, due to the yield stress, do not fully transmit the pressure to the outlet of the annular space. Sensibility analyses are then conducted in order to evaluate the thixotropic effect in pressure transmission.

Análise e proposição de estratégias de estimação e controle de velocidade para motores de indução trifásicos

This study presents a proposal of speed servomechanisms without the use of mechanical sensors (sensorless) using induction motors. A comparison is performed and propose techniques for pet rotor speed, analyzing performance in different conditions of speed and load. For the determination of control technique, initially, is performed an analysis of the technical literature of the main control and speed estimation used, with their characteristics and limitations. The proposed technique for servo sensorless speed induction motor uses indirect field-oriented control (IFOC), composed of four controllers of the proportional-integral type (PI): rotor flux controller, speed controller and current controllers in the direct and quadrature shaft. As the main focus of the work is in the speed control loop was implemented in Matlab the recursive least squares algorithm (RLS) for identification of mechanical parameters, such as moment of inertia and friction coefficient. Thus, the speed of outer loop controller gains can be self adjusted to compensate for any changes in the mechanical parameters. For speed estimation techniques are analyzed: MRAS by rotóricos fluxes MRAS by counter EMF, MRAS by instantaneous reactive power, slip, locked loop phase (PLL) and sliding mode. A proposition of estimation in sliding mode based on speed, which is performed a change in rotor flux observer structure is displayed. To evaluate the techniques are performed theoretical analyzes in Matlab simulation environment and experimental platform in electrical machinery drives. The DSP TMS320F28069 was used for experimental implementation of speed estimation techniques and check the performance of the same in a wide speed range, including load insertion. From this analysis is carried out to implement closed-loop control of sensorless speed IFOC structure. The results demonstrated the real possibility of replacing mechanical sensors for estimation techniques proposed and analyzed. Among these, the estimator based on PLL demonstrated the best performance in various conditions, while the technique based on sliding mode has good capacity estimation in steady state and robustness to parametric variations.

Nutritional profile and yield of oyster mushroom cultivated on selected agricultural wastes

Research on mushroom production and products is gaining more grounds globally and in particular Nigeria. This study was carried out to determine nutritional relationship between the substrate used for cultivation and the fruiting body on each of the substrates. Agro-wastes, namely: palm ( Elaeis guineensis ) fruit shaft, plantain ( Musa paradisiaca ) leaves, sawdust and kenaf ( Hibiscus cannabinus ) stem, were assessed for suitability as substrates for cultivation of oyster mushroom ( Pleurotus floridanus Singer ). The spawn of the mushroom was used to inoculate each of the substrates, using a complete randomised design, with five replicates for each substrate. Results showed that all the substrates supported mycelia growth and development of fruiting bodies of the fungus. There were significant differences (P<0.05) among substrates in terms of number of days to complete mycelia run, with the least recorded in palm fruit shaft (25.20), and the highest in kenaf (32.40). Total yield also differed significantly (P<0.05), with the highest in palm fruit shaft (51.4 g 100 g-1) and lowest in plantain leaves (6.0 g 100 g-1). There was also significant difference (P<0.05) in the nutritional content of fruiting bodies, the highest fat content being on plantain leaves (1.72 g 100 g-1) and the lowest on palm fruit shaft (0.55 g 100 g-1). The trend was similar for mushroom substrates, plantain leaves having (2.55 g 100 g-1) and palm fruit shaft, (0.41g 100 g-1). Starch content for fruiting bodies was highest on sawdust (5.31 g 100 g-1) and lowest on kenaf (2.66 g 100 g-1), while for mushroom substrates, kenaf was (0.33g 100 g-1) and palm fruit shaft was (4.45g 100 g-1). There was a positive correlation (r = 0.24) between the nutrient of fruiting bodies and that of the substrate on which it was cultivated.

Otimização de controle de tráfego em grupo de elevadores com algoritmos bioinspirados

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2015.

Do acesso clássico à comercialização: especificidades do mercado imobiliário informal na área especial de interesse social de Mãe Luiza, Natal/ RN.

This study presents research regarding affordable housing and their effects on the spatial reconfiguration of Natal/ RN, aiming to identify the specificities of the informality of urban land. This study aims to understand how informal housing market operates housing provision for the population located in popular informal settlements, through buying and selling market and rental market of residential properties irregular / illegal. This understanding will be through the neighborhood of Mãe Luisa, Special Area of Social Interest (SASI), located between neighborhoods with a population of high purchasing power and inserted into the tourist shaft of seaside of town. The characterization of informal housing market in Mãe Luiza, from buyers, sellers and renters, will help to understand how these informal transactions operate on SASI and housing provision for public policy development and implementation of housing programs and land regularization for low-income population, adequate to dynamic and reality of housing of informal areas

Penile Skin Involvement as the First Presentation of Henoch-Schonlein Purpura Report of Nine Cases and Review of Literature

Introduction: Involvement of penis is a rare presentation in henoch-schonlein purpura (HSP). The presentations are mainly due to the deposition of immunoglobulin A (IgA) into the vessel walls. In this report, we present the clinical history of nine HSP cases that presented with penile skin involvement. Case Presentation: All patients were referred in the acute phase of HSP. Penile skin involvement was evident as erythema, edema, ecchymosis, or induration of prepuce and/or penile shaft, that appeared simultaneously with skin rash in seven patients. Gastrointestinal involvement was positive in six patients. Patients were treated with steroids and follow up visits were normal except for one patient that developed crescentic glomerulonephritis. Conclusions: We present nine cases of HSP with penile involvement in order to indicate another rare aspect of HSP and its possible complications as well as its appropriate treatment.