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- An integrated test bench for research, study or demonstration of variable speed drives of induction motorsPublication . Teixeira, Henrique José Alves; Leite, Vicente; Batista, José; Araújo, Rui Esteves; Freitas, Diamantino SilvaThis paper presents an integrated and low cost test bench for teaching and R&D purposes in variable speed drives of induction motors. The test bench is composed by different integrated sub-systems and the resulting platform is suitable for control, parameter estimation and condition monitoring of induction machines controlled by electrical drives
- One dimensional consolidation properties of solid using incremental loading test : experimental setup based on a labview approachPublication . Gonçalves, José; Batista, José; Paula, António Miguel; Braz-César, ManuelThis work describes an experimental setup that was developed in order to automate the Onedimensional consolidation properties of soil test. This experimental setup assures repeatability in the data acquisition test, avoiding human errors. The described setup is based on LabVIEW, LVDT sensors, a 16 Bit Data Acquisition Board, a Load device and a Consolidometer. The experimental setup was developed according to the standard ASTM D2435 / D2435M - 11.
- Photovoltaic water pumping system for small power conventional AC pumpsPublication . Tangerino, Bruno Henrique Boschetti; Roman, Dionizio José Vargas; Leite, V.; Goedtel, Alessandro; Ferreira, Ângela P.; Batista, José; Maidana, WellingtonThe interest of photovoltaic (PV) water pumping systems with standard components is increasing as a low cost and independent solution over dedicated systems. However, one of the challenges of this alternative is the fact that small power systems to drive power pumps require a small number of PV modules and the PV string voltage is, usually, not enough to feed the frequency converter. This paper presents an approach to the drive, using a DC/DC converter with maximum power point tracking (MPPT). The overall system has been tested on a real experimental platform.
- Estudo de aplicabilidade do ensino edométrico a uma areia siltosaPublication . Paula, António Miguel; Gonçalves, José; Batista, José; Braz-César, Manuel; Freitas, Bruno AfonsoO presente artigo expõe o estudo de aplicabilidade do ensaio edométrico a uma areia siltosa, existente na cidade de Bragança, sendo que objetiva a aplicabilidade do ensaio aos solos de granulometria mais fina da região, com a ressalva de que a curva granulométrica destes se afasta de forma substancial das curvas granulométricas dos solos que por norma são alvo do ensaio edométrico. Objetiva assim o artigo, a aplicabilidade do ensaio aos solos mais finos oriundos de uma região com predominância de maciço residual granítico. Para tal, foram recolhidas amostras de dois solos com acentuada percentagem de finos, no contexto da predominância de solos da região, nomeadamente amostras indeformadas de uma areia siltosa, e amostras remexidas de um solo, posteriormente peneirado, com 100% de passados no peneiro nº 10, cuja granulometria corresponderá a um silte de elevada plasticidade. Devido à maior predominância de finos no silte de elevada plasticidade, o comportamento mecânico deste solo, mais condicionado por forças de natureza eletroquímica, representativo do comportamento dos solos finos, servirá de termo comparativo ao comportamento mecânico das amostras indeformadas de areia siltosa, com comportamento menos dependente destas forças, permitindo assim evidenciar a aplicabilidade do ensaio a solos de amostras indeformadas, com menor percentagem de finos, com comportamento gravítico mais acentuado e, portanto, mais atípicos a este ensaio devido à predominância de grossos na sua constituição. Dos resultados obtidos para a areia siltosa, verificou-se um elevado valor do assentamento imediato, após aplicação de cada ciclo de carga. Dado que a correta identificação do início do processo de consolidação carece de rigor no registo dos tempos de assentamento, fundamental para aplicação das metodologias de cálculo do ensaio, evidencia-se a necessidade de automatização de registo que minimize erros por parte de operadores humanos. Assim o recurso a um sistema de aquisição de dados revelou-se fundamental na identificação do início da consolidação primária, permitindo assim o alargar do espetro de aplicabilidade do ensaio.
- Grid-connection approaches for pico-hydro systemsPublication . Leite, V.; Ferreira, Ângela P.; Couto, José; Batista, JoséSmall hydropower systems are considered an environmentally friendly energy option. They have a huge untapped potential which allow it to make a more significant contribution to future energy demand with many advantages. Grid-connected pico-hydro systems are an emerging solution for application in a huge number of applications such as in household water supply, wastewater treatment facilities and to improve control systems and optimize generation as a part of integrated water management systems. They are also very promising for integration in microgrids in many developing countries. This paper presents and discusses the main three grid-connection approaches for pico-hydro systems: using specifically designed power converters; using standard wind inverters; and using standard photovoltaic inverters. These latest approaches based on conventional inverters are practical solutions able to explore a large amount of feasible sites with low-head and very low-head. Moreover, photovoltaic micro inverters, recently launched in the market, are propose for very low power generators (250-300 W). These approaches improve efficiencies, reduce costs and environmental impacts and improve reliability. Experimental evaluation of the performance in steady-state and in dynamic conditions proves the feasibility of these innovative approaches.
- Fully-automated strength, agility and endurance tests assessment: an integrated low cost approach based on an instrumented chairPublication . Gonçalves, José; Batista, José; Costa, Paulo Gomes daIn this paper it is described the prototyping of an instrumented chair that allows to fully-automate the ``Timed Up and Go'', the ``30-Second Chair Stand'' and the ``Hand-Force '' tests assessment. The presented functional chair prototype is a low cost approach that uses inexpensive sensors and the Arduino platform as the data acquisition board, with its software developed in LabVIEW. The ``Timed up and go test'' consists in measuring the time spent in the task execution of standing up from a chair, walk three meters with a maximum speed without running, turn a cone and going back to the initial position. The ``30-Second Chair Stand'' test consists in counting the number of completed chair stands in 30 seconds. It are agility, strength and endurance tests easy to setup and execute although they lack of repeatability, whenever the measures are taken manually, due to the rough errors that are introduced. The ``Hand-Force'' test consists in measuring the hand strength, the relevant data are the peak and average values of several tests. The referred data is important in order to evaluate hand rehabilitation treatment results.
- Validation with videometry of an integrated system to assess horizontal intra-cyclic velocity with a mechanical speedo-meterPublication . Barbosa, Tiago M.; Costa, M.J.; Morais, J.E.; Jesus, Sérgio; Silva, A.J.; Batista, José; Gonçalves, JoséThe aim of this paper was to: validate an integrated system (i.e., software application and hardware after calibration) to assess human’s horizontal intra-cyclic velocity with a mechanical speedo-meter. System validation was done for a set of land-based human locomotion techniques (from slow walk to maximal running) in four subjects and comparing it with a videometric system (i.e. APAS). There were no significant differences between pair wise data (speedo-meter versus APAS data) using student‘s t-test for both velocity coefficient of variation and maximal velocity. Linear regression models where very high for both the velocity coefficient of variation and maximal velocity. More than 80% of the Bland-Altman plots were within 1.96 standard-deviations.
- Validation of an integrated system to assess horizontal intra-cyclic velocity with a mechanical speedo-meterPublication . Barbosa, Tiago M.; Costa, M.J.; Morais, J.E.; Jesus, Sérgio; Silva, A.J.; Batista, José; Gonçalves, JoséThe aim of this paper was to: validate an integrated system (i.e., software application and hardware after calibration) to assess human’s horizontal intra-cyclic velocity with a mechanical speedo-meter.
- Low-cost I-V tracer for photovoltaic modules and stringsPublication . Leite, V.; Batista, José; Chenlo, Faustino; Afonso, João L.This paper presents new developments of a robust and low-cost instrument - less than 600 € - for monitoring and processing I-V and P-V characteristics of photovoltaic (PV) modules and high voltage strings. The characteristics can be traced on an oscilloscope or using a developed a LabVIEW application. It is a simple instrument because only fundamental electronic circuits are used. The equipment consists of a flexible configuration, developed from a previous work, based on a fast varying load based on a power MOSFET. The MOSFET was controlled by means of suitable gate-source voltage control signal in order to improve the tracing of I-V and P-V characteristics on an oscilloscope. The contribution of this work includes new developments of a previous I-V tracer in order to be use with high voltage strings and a low-cost DAQ monitoring system based on two applications developed in LabVIEW - one for PV modules and the other for PV strings. On the other hand, the robustness for high voltage strings was strongly improved in view of field tests for fault diagnosis analysis. Experimental results obtained with the new instrument are presented with modules and different strings available with voltages up to 1000 volt. © 2014 IEEE.
- Dealing with the very small: first steps of a picohydro demonstration project in an university campusPublication . Leite, Vicente; Figueiredo, Tomás de; Pinheiro, Tiago; Ferreira, Ângela P.; Batista, JoséThis paper presents the implementation, project and design of a small run-of-river hydropower plant, designed for demonstration purposes, under a Project aimed to be a framework of wide spread dissemination of renewable energies and energy efficiency in an University Campus. The details of the hydroelectric power plant, from the project design until the final use of the produced electric energy, are described. The main requirements of the implementation are presented, with regards to the environmental footprint and topography of the site and the adopted solutions are also described. Considering the demonstration purposes, two different electrical systems were installed in the power house: stand-alone and grid-connected. The latter establishes a case study in the development and application of picohydro power plants as microgeneration units in the context of distributed generation systems. The evaluation of both systems is also presented, based on the experimental results obtained from tests experiments and from monitoring the first months of operation at the site.