Desenvolvimento de algoritmo de controle de tração para regeneração de energia metroviária - ACTREM: melhoria da eficiência energética de sistemas de tração metroviária.

Esta tese propõe um modelo de regeneração de energia metroviária, baseado no controle de paradas e partidas do trem ao longo de sua viagem, com o aproveitamento da energia proveniente da frenagem regenerativa no sistema de tração. O objetivo é otimizar o consumo de energia, promover maior eficiência, na perspectiva de uma gestão sustentável. Aplicando o Algoritmo Genético (GA) para obter a melhor configuração de tráfego dos trens, a pesquisa desenvolve e testa o Algoritmo de Controle de Tração para Regeneração de Energia Metroviária (ACTREM), usando a Linguagem de programação C++. Para analisar o desempenho do algoritmo de controle ACTREM no aumento da eficiência energética, foram realizadas quinze simulações da aplicação do ACTREM na linha 4 - Amarela do metrô da cidade de São Paulo. Essas simulações demonstraram a eficiência do ACTREM para gerar, automaticamente, os diagramas horários otimizados para uma economia de energia nos sistemas metroviários, levando em consideração as restrições operacionais do sistema, como capacidade máxima de cada trem, tempo total de espera, tempo total de viagem e intervalo entre trens. Os resultados mostram que o algoritmo proposto pode economizar 9,5% da energia e não provocar impactos relevantes na capacidade de transporte de passageiros do sistema. Ainda sugerem possíveis continuidades de estudos.

Real time optimization in chemical process: evaluation of strategies, improvements and industrial application.

The increasing economic competition drives the industry to implement tools that improve their processes efficiencies. The process automation is one of these tools, and the Real Time Optimization (RTO) is an automation methodology that considers economic aspects to update the process control in accordance with market prices and disturbances. Basically, RTO uses a steady-state phenomenological model to predict the process behavior, and then, optimizes an economic objective function subject to this model. Although largely implemented in industry, there is not a general agreement about the benefits of implementing RTO due to some limitations discussed in the present work: structural plant/model mismatch, identifiability issues and low frequency of set points update. Some alternative RTO approaches have been proposed in literature to handle the problem of structural plant/model mismatch. However, there is not a sensible comparison evaluating the scope and limitations of these RTO approaches under different aspects. For this reason, the classical two-step method is compared to more recently derivative-based methods (Modifier Adaptation, Integrated System Optimization and Parameter estimation, and Sufficient Conditions of Feasibility and Optimality) using a Monte Carlo methodology. The results of this comparison show that the classical RTO method is consistent, providing a model flexible enough to represent the process topology, a parameter estimation method appropriate to handle measurement noise characteristics and a method to improve the sample information quality. At each iteration, the RTO methodology updates some key parameter of the model, where it is possible to observe identifiability issues caused by lack of measurements and measurement noise, resulting in bad prediction ability. Therefore, four different parameter estimation approaches (Rotational Discrimination, Automatic Selection and Parameter estimation, Reparametrization via Differential Geometry and classical nonlinear Least Square) are evaluated with respect to their prediction accuracy, robustness and speed. The results show that the Rotational Discrimination method is the most suitable to be implemented in a RTO framework, since it requires less a priori information, it is simple to be implemented and avoid the overfitting caused by the Least Square method. The third RTO drawback discussed in the present thesis is the low frequency of set points update, this problem increases the period in which the process operates at suboptimum conditions. An alternative to handle this problem is proposed in this thesis, by integrating the classic RTO and Self-Optimizing control (SOC) using a new Model Predictive Control strategy. The new approach demonstrates that it is possible to reduce the problem of low frequency of set points updates, improving the economic performance. Finally, the practical aspects of the RTO implementation are carried out in an industrial case study, a Vapor Recompression Distillation (VRD) process located in Paulínea refinery from Petrobras. The conclusions of this study suggest that the model parameters are successfully estimated by the Rotational Discrimination method; the RTO is able to improve the process profit in about 3%, equivalent to 2 million dollars per year; and the integration of SOC and RTO may be an interesting control alternative for the VRD process.

Controlador integrado baseado em conceito híbrido e controle geométrico para embarcações posicionadas dinamicamente.

O conceito de controle híbrido é aplicado à operação de alívio entre um FPWSO e um navio aliviador. Ambos os navios mantêm suas posições e aproamentos pelo resultado da ação do seu Sistema de Posicionamento Dinâmico (SPD). O alívio dura cerca de 24 horas para ser concluído. Durante este período, o estado de mar pode se alterar e os calados estão sendo constantemente alterados. Um controlador híbrido é projetado para permitir modificacões dos parâmetros de controle/observação se alguma alteração significante do estado de mar e/ou calado das embarcações ocorrer. O principal objetivo dos controladores é manter o posicionamento relativo entre os navios com o intuito de evitar perigosa proximidade ou excesso de tensão no cabo. Com isto em mente, uma nova estratégia de controle que atue integradamente em ambos os navios é proposta baseda em geometria diferencial. Observadores não lineares baseados em passividade são aplicados para estimar a posição, a velocidade e as forças externas de mares calmos até extremos. O critério para troca do controle/observação é baseado na variação do calado e no estado de mar. O calado é assumido conhecido e o estado de mar é estimado pela frequência de pico do espectro do movimento de primeira ordem dos navios. Um modelo de perturbação é proposto para encontrar o número de controladores do sistema híbrido. A equivalência entre o controle geométrico e o controlador baseado em Multiplicadores de Lagrange é demonstrada. Assumindo algumas hipóteses, a equivalência entre os controladores geométrico e o PD é também apresentada. O desempenho da nova estratégia é avaliada por meio de simulações numéricas e comparada a um controlador PD. Os resultados apresentam muito bom desempenho em função do objetivo proposto. A comparação entre a abordagem geométrica e o controlador PD aponta um desempenho muito parecido entre eles.

Spectral BRDF-based determination of proper measurement geometries to characterize color shift of special effect coatings

A reduced set of measurement geometries allows the spectral reflectance of special effect coatings to be predicted for any other geometry. A physical model based on flake-related parameters has been used to determine nonredundant measurement geometries for the complete description of the spectral bidirectional reflectance distribution function (BRDF). The analysis of experimental spectral BRDF was carried out by means of principal component analysis. From this analysis, a set of nine measurement geometries was proposed to characterize special effect coatings. It was shown that, for two different special effect coatings, these geometries provide a good prediction of their complete color shift.

Event-based visual servoing

Traditional visual servoing systems have been widely studied in the last years. These systems control the position of the camera attached to the robot end-effector guiding it from any position to the desired one. These controllers can be improved by using the event-based control paradigm. The system proposed in this paper is based on the idea of activating the visual controller only when something significant has occurred in the system (e.g. when any visual feature can be loosen because it is going outside the frame). Different event triggers have been defined in the image space in order to activate or deactivate the visual controller. The tests implemented to validate the proposal have proved that this new scheme avoids visual features to go out of the image whereas the system complexity is reduced considerably. Events can be used in the future to change different parameters of the visual servoing systems.

Event-based visual servoing with features’ prediction

Event-based visual servoing is a recently presented approach that performs the positioning of a robot using visual information only when it is required. From the basis of the classical image-based visual servoing control law, the scheme proposed in this paper can reduce the processing time at each loop iteration in some specific conditions. The proposed control method enters in action when an event deactivates the classical image-based controller (i.e. when there is no image available to perform the tracking of the visual features). A virtual camera is then moved through a straight line path towards the desired position. The virtual path used to guide the robot improves the behavior of the previous event-based visual servoing proposal.

Control of Redundant Joint Structures Using Image Information During the Tracking of Non-Smooth Trajectories

Visual information is increasingly being used in a great number of applications in order to perform the guidance of joint structures. This paper proposes an image-based controller which allows the joint structure guidance when its number of degrees of freedom is greater than the required for the developed task. In this case, the controller solves the redundancy combining two different tasks: the primary task allows the correct guidance using image information, and the secondary task determines the most adequate joint structure posture solving the possible joint redundancy regarding the performed task in the image space. The method proposed to guide the joint structure also employs a smoothing Kalman filter not only to determine the moment when abrupt changes occur in the tracked trajectory, but also to estimate and compensate these changes using the proposed filter. Furthermore, a direct visual control approach is proposed which integrates the visual information provided by this smoothing Kalman filter. This last aspect permits the correct tracking when noisy measurements are obtained. All the contributions are integrated in an application which requires the tracking of the faces of Asperger children.

μ-MAR: Multiplane 3D Marker based Registration for depth-sensing cameras

Many applications including object reconstruction, robot guidance, and. scene mapping require the registration of multiple views from a scene to generate a complete geometric and appearance model of it. In real situations, transformations between views are unknown and it is necessary to apply expert inference to estimate them. In the last few years, the emergence of low-cost depth-sensing cameras has strengthened the research on this topic, motivating a plethora of new applications. Although they have enough resolution and accuracy for many applications, some situations may not be solved with general state-of-the-art registration methods due to the signal-to-noise ratio (SNR) and the resolution of the data provided. The problem of working with low SNR data, in general terms, may appear in any 3D system, then it is necessary to propose novel solutions in this aspect. In this paper, we propose a method, μ-MAR, able to both coarse and fine register sets of 3D points provided by low-cost depth-sensing cameras, despite it is not restricted to these sensors, into a common coordinate system. The method is able to overcome the noisy data problem by means of using a model-based solution of multiplane registration. Specifically, it iteratively registers 3D markers composed by multiple planes extracted from points of multiple views of the scene. As the markers and the object of interest are static in the scenario, the transformations obtained for the markers are applied to the object in order to reconstruct it. Experiments have been performed using synthetic and real data. The synthetic data allows a qualitative and quantitative evaluation by means of visual inspection and Hausdorff distance respectively. The real data experiments show the performance of the proposal using data acquired by a Primesense Carmine RGB-D sensor. The method has been compared to several state-of-the-art methods. The results show the good performance of the μ-MAR to register objects with high accuracy in presence of noisy data outperforming the existing methods.

Kinetic Model for Micro Algae Cell Concentration and Size Distribution: Application to Nannochloropsis gaditana

The cell concentration and size distribution of the microalgae Nannochloropsis gaditana were studied over the whole growth process. Various samples were taken during the light and dark periods the algae were exposed to. The distributions obtained exhibited positive skew, and no change in the type of distribution was observed during the growth process. The size distribution shifted to lower diameters in dark periods while in light periods the opposite occurred. The overall trend during the growth process was one where the size distribution shifted to larger cell diameters, with differences between initial and final distributions of individual cycles becoming smaller. A model based on the Logistic model for cell concentration as a function of time in the dark period that also takes into account cell respiration and growth processes during dark and light periods, respectively, was proposed and successfully applied. This model provides a picture that is closer to the real growth and evolution of cultures, and reveals a clear effect of light and dark periods on the different ways in which cell concentration and diameter evolve with time.

Teaching as a fractal: from experience to model

The aim of this work is to improve students’ learning by designing a teaching model that seeks to increase student motivation to acquire new knowledge. To design the model, the methodology is based on the study of the students’ opinion on several aspects we think importantly affect the quality of teaching (such as the overcrowded classrooms, time intended for the subject or type of classroom where classes are taught), and on our experience when performing several experimental activities in the classroom (for instance, peer reviews and oral presentations). Besides the feedback from the students, it is essential to rely on the experience and reflections of lecturers who have been teaching the subject several years. This way we could detect several key aspects that, in our opinion, must be considered when designing a teaching proposal: motivation, assessment, progressiveness and autonomy. As a result we have obtained a teaching model based on instructional design as well as on the principles of fractal geometry, in the sense that different levels of abstraction for the various training activities are presented and the activities are self-similar, that is, they are decomposed again and again. At each level, an activity decomposes into a lower level tasks and their corresponding evaluation. With this model the immediate feedback and the student motivation are encouraged. We are convinced that a greater motivation will suppose an increase in the student’s working time and in their performance. Although the study has been done on a subject, the results are fully generalizable to other subjects.

The Labour Allocation Decisions of Farm Households: Defining a theoretical model. Factor Markets Working Paper No. 31, October 2012

This paper presents a theoretical model for the analysis of decisions regarding farm household labour allocation. The agricultural household model is selected as the most appropriate theoretical framework; a model based on the assumption that households behave to maximise utility, which is a function of consumption and leisure, and is subject to time and budget constraints. The model can be used to describe the role of government subsidies in farm household labour allocation decisions; in particular the impact of decoupled subsidies on labour allocation can be examined. Decoupled subsidies are a labour-free payment and as such represent an increase in labour-free income or wealth. An increase in wealth allows farm households to work less while maintaining consumption. On the other hand, decoupled subsidies represent a decline in the return to farm labour and may lead to a substitution effect, i.e., farmers may choose to substitute non-farm work for farm work. The theoretical framework proposed in this paper allows for the examination of these two conflicting effects.

Aplicações baseadas em geolocalizações para gestão de instalações desportivas: exemplo de utilização da API da GOOGLE Maps no concelho de Guimarães

O contexto tecnológico em que vivemos é uma realidade. E a tendência é para ser assim também no futuro. Cada vez mais. É o caso das representações de locais e entidades em mapas digitais na web. Na visão de Crocker (2014), esta tendência é ainda mais acentuada, no âmbito das aplicações móveis, como mostram as mais diversas location-based applications. No setor do desporto e da respetiva gestão nem sempre foi fácil desenvolver aplicações, recorrendo a este tipo de representações espaciais. A tecnologia não era fácil e o know-how não era adequadamente qualificado. Mas, as empresas fornecedoras de tecnologia geoespacial simplificaram o desenvolvimento de aplicações web nesta área, através da utilização de application programming interfaces (API). Como refere Svennerberg (2010), estas API’s servem de interface entre um serviço proporcionado por uma empresa, caso da Google Maps (2013) e uma aplicação web ou móvel que utiliza esses serviços. Foi com este objetivo que desenvolvemos uma aplicação web, utilizando as metodologias próprias neste domínio, como a framework de Zachman (2009), tal como foi originalmente adaptada por Whitten e Bentley (2005), onde um dos módulos é precisamente a representação de espaços desportivos, recorrendo à utilização dos serviços da Google Maps. Para além disso, toda a aplicação é suportada numa abordagem Model-View-Control (MVC). Para conseguir representar as instalações desportivas num mapa, criámos uma base de dados MySQL, com dados de longitude e latitude, de cada instalação desportiva. Através de JavaScript criou-se o mapa propriamente dito, indicando o tipo (mapa de estradas, satélite ou street view) e as respetivas opções (nível de zoom, alinhamento, controlo de interface e posicionamente, entre muitas outras opções). O passo seguinte consistiu em passar os dados para o frontend da aplicação web. Para isso, recorreu-se à integração do PHP com as livrarias externas de código JavaSrcipt, criadas especificamente para o efeito (caso da MarkerManager). A implementação destas funcionalidades permite georeferenciar todos os tipos e géneros de espaços desportivos de um concelho, região ou País. Obteve-se ainda know-how, background e massa crítica, para o desenvolvimento de novas funcionalidades. A sua utilização em dispositivos móveis é outra das possibilidades atualmente já em desenvolvimento.

(Table 1) Gravity and pressure within the Sleipner area relative to ones at the reference station in 2002 and 2005

At Sleipner, CO2 is being separated from natural gas and injected into an underground saline aquifer for environmental purposes. Uncertainty in the aquifer temperature leads to uncertainty in the in situ density of CO2. In this study, gravity measurements were made over the injection site in 2002 and 2005 on top of 30 concrete benchmarks on the seafloor in order to constrain the in situ CO2 density. The gravity measurements have a repeatability of 4.3 µGal for 2003 and 3.5 µGal for 2005. The resulting time-lapse uncertainty is 5.3 µGal. Unexpected benchmark motions due to local sediment scouring contribute to the uncertainty. Forward gravity models are calculated based on both 3D seismic data and reservoir simulation models. The time-lapse gravity observations best fit a high temperature forward model based on the time-lapse 3D seismics, suggesting that the average in situ CO2 density is about to 530kg/m**3. Uncertainty in determining the average density is estimated to be ±65 kg/m**3 (95% confidence), however, this does not include uncertainties in the modeling. Additional seismic surveys and future gravity measurements will put better constraints on the CO2 density and continue to map out the CO2 flow.

A Study of Shallow Groundwater Migration through Anthropogenic Fill along a Seawall

This report provides the findings and opinions of a historical document review, hydraulic balance calculation, and proposed additional study for a property that was historically used as a bulk petroleum storage and distribution facility. The property lies along the base, west, of a heavily vegetated bluff with a tidally influenced body of water west-adjacent to the property. The western portion of the property is bounded by a seawall spanning approximately 3,200 linear feet trending north-south. The seawall’s construction details are not known, save for a 225-foot section of driven sheet pile wall located within the northern portion of the property’s seawall. Due to the presence of petroleum hydrocarbons in soil and groundwater at the property, a cleanup action for the property will likely be overseen by the state regulatory agency. The property is currently undergoing remedial investigation in an effort to identify the lateral and vertical extent in which contaminants at the property have come to be located, also known as the “site” as defined by the Model Toxics Control Act (MTCA). The majority of the property bounded within the seawall area has been characterized; however, the shoreline sediments located immediately west-adjacent of the seawall have not been properly delineated. Identifying the bounds of the site to the west within sediment is pivotal for the purposes of the remedial investigation. Since the west-adjacent shoreline is so extensive, conducting a complete sediment sampling event along the entire shoreline would be cost-prohibitive due to analytical costs and logistical issues at the property. Because of the extensive nature of the shoreline, it would greatly benefit the client and project to focus sampling efforts at areas of greater risk for contaminants along the shoreline by identifying potential preferential pathways for contaminants to migrate off of the property and into adjacent shoreline sediments. The review of historical studies of the property yielded some useful information; however much of the findings included within the historical studies were lacking original raw data, therefore limiting the information obtained. The calculated hydraulic balance for the property yielded a relatively large surplus of recharge to groundwater after precipitation events, reinforcing the concept that contaminant have potentially historically, and currently, been migrating into the adjacent shoreline through preferential pathways along the seawall. Due to the limitation within the historical studies for the property as well as the groundwater recharge identified in the hydraulic balance, an additional study was proposed in an effort to provide additional aquifer characteristics along the seawall, and the ability to observe flow propagation at and proximate to the seawall in two-dimensions through time without the need to piece separate studies together. This proposed study includes a single simultaneous tidal study which comprises select monitoring points along the seawall. This report has identified the need for additional data that can be collected through available avenues for the property based upon the client’s desires and project needs. Ultimately, the proposed additional study is suggested based upon its relatively low capital investment, and ability meet the requirements relevant to the specific project needs and scope. Assuming preferential pathways are identified through the additional study proposed within this report, a representative and cost-effective sediment sampling plan can then be put in place in an effort to define the site.