Conceção, projeto e desenvolvimento de uma vitrina refrigerada de gelataria

O principal objetivo da vitrina refrigeradora para gelatarias é garantir a conservação dos gelados, bem como mantê-los com a textura desejada. Este objetivo é garantido através da imposição de um intervalo de temperaturas dentro do qual a vitrina se deve manter. A norma portuguesa NP3293 de 2008 indica que os gelados devem ser mantidos a temperaturas iguais ou inferiores a -18°C e nunca ultrapassar os -15°C, no entanto, as vitrinas existentes apresentam na sua maioria problemas em manter este intervalo de temperaturas em todo o seu volume útil. Neste artigo é apresentado de forma detalhada o estudo e desenvolvimento de uma nova vitrina de gelataria. Este equipamento deve garantir a qualidade dos gelados, mantendo-os a uma temperatura de -18ºC. No intuito de otimizar a eficiência energética, foi analisado o fluido refrigerante a utilizar, tendo-se optado pelo R507 apesar de ser diferente do habitual. A minimização da carga térmica implicou uma cuidada seleção dos componentes e isolamentos. Todo o controlo do sistema, garantido através de um PLC, foi concebido, projetado e desenvolvido no sentido de permitir a melhor eficiência energética do compressor e da ventoinha do condensador, de acordo com a temperatura lida no interior da vitrina.The main objective of the shop ice cream refrigerator is to guarantee the conservation of ice creams, as well as, to maintain them with the wanted texture. This objective is guaranteed through the imposition of a temperature interval to the shop ice cream refrigerator. The Portuguese norm NP3293 2008 indicates that the ice creams should be maintained to temperatures same or inferior to -18°C and never to cross the -15°C, however, the existent shop ice cream refrigerator present in its majority problems to maintain this temperature interval. This article present, in a detailed way, the study and development of a new shop ice cream refrigerator. This equipment should guarantee the ice creams quality, maintaining them to a temperature of -18ºC. To optimize the energy efficiency, the cooling fluid was analyzed, having chosen the R507 in spite of being different from the usually used. In order to minimize the thermal load it was realized a carefully selection of components and of thermal and acoustic isolations. The control system, guaranteed through a PLC, it was designed and developed with the purpose of allowing the best energy efficiency of compressor and condenser fan, in agreement with the shop ice cream refrigerator temperature

Engineering students’ perspective on their learning experience in Higher Education: Findings from a pilot study

Understanding the ways in which students at higher education live and assess their learning experiences is a key issue in improving the education and development opportunities provided to them, especially in times of change and challenge. This work draws upon data taken from broader and ongoing research project aimed to investigating engineering students’ perspectives on teaching and learning in higher education. Data were colleted through questionnaires administrated at the end of the semester in module ‘Biomechanics’ (45 hours per semester). The questionnaire included the following dimensions: motivation for entering an engineering degree, teaching methods, assessment procedures, teacher’s performance, classroom climate, content, timetable, resources and equipment. Preliminary findings suggest that, by and large, students enjoyed both the diversity of the learning activities and content of the module. They also highlighted the key importance of the teacher/student relationship. However, issues such as intrinsic motivation, student participation in defining assessment procedures and the available resources (including time) and equipment emerged in explaining both similarities and differences in students’ responses. These will be discussed further in the paper.The authors would like to express their gratitude to all those who have collaborated and contributed to the concretization of this study, namely to the Medical Engineering students who have responded to the questionnaire. The second author expresses his gratitude to Portuguese Foundation for the Science and Technology for the postdoctoral scholarship (SFRH/BPD/77831/2011)

Teaching kinematics and dynamics of multibody mechanical systems using the object oriented language modelica

A new modeling language, called Modelica, for physical modeling is being developed in an international effort. The main objective is to make it easy to exchange models and model libraries for different domains, such as, mechanical, pneumatics, electrical, hydraulics, and others. The design approach builds on non-causal modeling with true ordinary differential and algebraic equations and the use of object-oriented constructs stemming from modern software development, (hierarchy, encapsulation) to facilitate reuse of models and model parts. This paper gives an overview of the use of the object oriented language Modelica with the mechanical Multibody Library to model and simulate three-dimensional mechanical systems

Using advanced simulation techniques to improve industrial controller’s dependability

Modelica Modeling language is powerful and suitable for modeling mechatronic systems, being possible to interact different technological aspects and deal, simultaneously with different technologies (mechanical, electrical, pneumatic, hydraulic,..). In this paper it is discussed, in a case study, the possibility of using this language for modeling an automation system (controller and plant) in closed loop behavior and also in defining some parameters of the automation system in order to optimize some behavior aspects of the system as, for instance, the time cycle of the automation system. Some aspects relied with controllers dependability are also discussed and it is showed how Modelica modeling language can help controllers’ designers improving controllers dependability, when are used Simulation Techniques

Design of an adapted standing frame for rehabilitation of children with mental deficiency

A standing frame is a mechanical (old) or mechatronic (new) equipment, that has as main goal to correct the incapacity of certain individuals for assuming the body’s vertical position. The existing standing frames, on the market, do not allow easy placement of the patient on the device, do not allow full mobility (within and outside of buildings), they are not versatile, they are not modular and they do not allow children to have occupational activities during treatments. This paper presents the project of a Standing frame for use in the treatment of children with mental deficiency. The Standing frame presented in this paper takes into account the limitations mentioned above and is perfectly adapted to this very specific and very special target people. The main features of the equipment whose project is presented in this article are the modularity, easiness of placing the patient and easiness of use, especially when the patient, and family, need to travel and need to carry with them the standing frame.(undefined

Automação do processo de verificação de software para programadores lógicos SIL em aplicações de exploração de petróleo submarina

Process Shutdown systems are used for shutting down subsea oil and gas wells and maintaining a safe state for the intervention systems. The safety and reliability of the technology used for process shutdown is one of the major arguments to earn the trust of the customer and consequently one of the main technological reasons to stay ahead of the subsea oil and gas business market. SIL (IEC61508) is the measure of trust. This is where SIL certified logic solvers come into play. For every project using SIL logic solvers specific software has to be made based on applicable standards and customer shutdown philosophies. Before deployment the system has to be verified. The intention is to apply new methods for automating the testing of the software. This will provide run-time improvement of testing, reduction of the needed resources and direct reduced costs in ongoing projects.Sistemas de encerramento do processo são usados para parar a produção dos poços de petróleo e gás e manter em segurança a funcionalidade dos sistemas de intervenção. A segurança e a confiabilidade da tecnologia utilizada para a paragem da produção é um dos principais argumentos para ganhar a confiança do cliente e, consequentemente uma das principais razões tecnológicas para continuar na vanguarda do mercado de exploração submarina de petróleo e gás. É aqui que entram os programadores lógicos com certificação SIL. Para cada projeto que utilize programadores lógicos SIL software específico tem que ser criado com base na normalização aplicável e nas filosofias de encerramento de processo. Antes do fornecimento do equipamento de segurança a funcionalidade do sistema tem que ser verificada. A intenção é aplicar novos métodos para automatizar a verificação do software. Isso permite melhoria no tempo de execução dos testes, redução dos recursos necessários e redução de custos nos projectos em curso.info:eu-repo/semantics/publishedVersio

Oil-hydraulic power units - state of the art

Despite the evolution of electric drives and their undeniable advantages, hydraulic systems play an important role in today's technologies. Due to the ability to operate enormous power densities, industrial hydraulics are irreplaceable when large forces and binaries are required. Its importance can be characterized by the economy it represents and by the development potential associated with scientific interest. This paper summarizes the technologies used in the production of oil-hydraulic power, seeking to identify the trends of development and the research opportunities that come from the demands of the current developments.info:eu-repo/semantics/publishedVersio

Use Arduino as a modbus slave over RTU

The purpose of this article is to accomplish various appointed objectives. The objectives of this article include: to become acquainted with the Modbus RTU protocol, to implement the Modbus RTU protocol onto an Arduino Uno microcontroller as a slave and to test the Arduino Uno slave using a free Modbus master program. The Arduino Uno slave must be fully configurable where the user can set all the Modbus communication parameters such as slave ID, parity, communication rate, number of stop bits, etc. The user must also be able to assign values or variables to a particular coil or register regardless of the order of the previously used coils or registers. The Arduino slave must also communicate with the master over a RS232 connection.info:eu-repo/semantics/publishedVersio

Machine and mechanism design at UMinho: research-teaching interaction

Publicado em: "New trends in mechanism and machine science: from fundamentals to industrial applications. ISBN 978-3-319-09410-6. Series: Mechanisms and machine science, vol. 24, ISSN 2211-0984"The Multiweave project involved the design of a prototype machine with several mecha-nisms, namely gear trains and various conjugate cams with oscillating roller followers. For this design phase the research team integrated postgraduate student work. In order to evaluate the quality of the manufactured cam profiles as well as the accuracy of the follower’s displacement, an experimental work has been designed. This study, which was carried out within a final year Mechanical Engineering student’s group project, was of great importance in the development of the prototype machine to pro-duce multidirectional woven fabrics, which was the main objective of the Multiweave project. The whole set-up is presented with the experimental details and the results are analysed and discussed. This measurement system is based on a laser triangulation sensor Micro-Epsilon ILD 1302-50 to measure with no contact and high resolution. The obtained results were compared with the expected theoretical values and it could be concluded that, in general, the experimental results adjust very well to the theo-retical ones. However it was possible to conclude about the existence of some differences due to clear-ances in joints, geometric differences in the kinematic chain and manufacturing defects on the follower in terms of irregularities and surface roughness as well as some manufacturing imperfections of the cam surface

Property patterns for the formal verification of automated production systems

In recent years, several approaches to the analysis of automation systems dependability through the application of formal verification techniques have been proposed. Much of the research has been concerned with the modelling languages used, and how best to express the automation systems, so that automated verification might be possible. Less attention, however, has been devoted to the process of writing properties that accurately capture the requirements that need verification. This is however a crucial aspect of the verification process. Writing appropriate properties, in a logic suitable for verification, is a skilful process, and indeed there have been reports of properties being wrongly expressed. In this paper we put forward a tool and a collection of property patterns that aim at providing help in this area