ENIDH – EEM - Comunicações, Congressos, Seminários, Encontros, etc.
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- A 1.1 µA voltage reference circuit with high PSRR and temperature compensationPublication . Pereira, M. Silva; Costa, João E. N.; Santos, M.; Vaz, J. CaldinhasThis paper presents a low-power and a low output voltage CMOS Bandgap Reference Generator topology with high PSRR and a novel temperature curvature compensation method. The proposed design was implemented in a standard 0.13 μm CMOS process. The main circuit is based in an opamp based β-multiplier bandgap circuit with resistive division. The compensation method cancels out up to 2nd order non-linear terms of the BJT voltage by using the MOSFET leakage current effect. The performance of the circuit was verified by post-layout simulations. Simulated results have shown temperature coefficients as low as -4.4 ppm/°C over a temperature range of 140°C (-40°C to 100°C). In addition the circuit demonstrated a PSSR of -100 dB at low frequencies and -73 dB at 1 MHz. The current consumption is 1.1 μA at 27°C.
- Accomplishing PROMISE, PROgrammable MIxed Signal ASIC Electronics FrameworkPublication . Berrojo, Luis; Veljkovic, Filip; Ayzac, Philippe; Maggioni-Mezzomo, Cecilia; Trouche, Christophe; Kakoulin, Michael; Franciscatto, Giancarlo; Berti, Laurent; Arslanov, Dmitry; Póvoa, Ricardo; Guilherme, Jorge; Roumkou, Anna; Tukkiniemi, KariThis paper presents the activities, current results and status of the PROMISE (PROgrammable MIxed Signal Electronics) project which started at the beginning of 2020 . The project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 870358. It’s tailored to bring to the space community a flexible, cost competitive mixed-signal ASIC architecture design ecosystem built on a portfolio of silicon qualified hardened IP blocks. It includes analogue IPs such as ADC, DAC, PLL, LDO, BG, LO, POR and HV MOS transistors. A digital embedded FPGA core provides a flexible programmable element and an NVM permits reconfiguration abilities without the need of using an external memory. All these elements are included on the PILOT Circuit ASIC that will be submitted to electrical validation and radiation testing as part of the qualification process of these basic elements for their future use as building blocks.
- Computing Repairs from Active Integrity ConstraintsPublication . Cruz-Filipe, L.; Engrácia, P.; Nunes, I.; Gaspar, G.Repairing an inconsistent knowledge base is a well known problem for which several solutions have been proposed and implemented in the past. In this paper, we start by looking at databases with active integrity constraints - consistency requirements that also indicate how the database should be updated when they are not met - as introduced by Caroprese et al.We show that the different kinds of repairs considered by those authors can be effectively computed by searching for leaves of specific kinds of trees. Although these computations are in general not very efficient (deciding the existence of a repair for a given database with active integrity constraints is NP-complete), on average the algorithms we present make significant reductions on the number of nodes in the search tree. Finally, these algorithms also give an operational characterization of different kinds of repairs that can be used when we extend the concept of active integrity constraints to the more general setting of knowledge bases.
- Description logics, rules and multi‐context systemsPublication . L. Cruz‐Filipe, l.; Henriques, R.; Nunes, I.The combination of rules and ontologies has been a fertile topic of research in the last years, with the proposal of several different systems that achieve this goal. In this paper, we look at two of these formalisms, Mdl-programs and multi-context systems, which address different aspects of this combination, and include different, incomparable programming constructs. Despite this, we show that every Mdl-program can be transformed in a multi-context system, and this transformation relates the different semantics for each paradigm in a natural way. As an application, we show how a set of design patterns for multi-context systems can be obtained from previous work on Mdl-programs.
- Dynamic Voltage-Combiners Biased OTA for Low-Power High-Speed SC CircuitsPublication . Póvoa, R.; Canelas, A.; Martins, R.; Lourenço, N.; Horta, N.; Goes, J.his paper presents the design of a fully-dynamic voltage-combiners biased CMOS operational transconductance amplifier, for low-power high-speed analog-to-digital converters and high-performance switched-capacitor filters, using the UMC 130nm node. The biasing is controlled by switched-capacitors and simulation results of an optimized solution using AIDA-C, a state-of-the-art multi-objective multi-constraint IC optimization tool, present a DC gain of 60.9dB, a gain-bandwidth product of 155.1MHz for a 6pF load and a current consumption of 0.69mArms for a sampling clock frequency of 100MHz.
- Edge Computing and Internet of Things Based Platform to Improve the Quality of Life of the Silver Economy on Leisure Cruise ShipsPublication . Plaza-Hernández, Marta; Sittón-Candanedo, Inés; Alonso, Ricardo S.; Martínez-de Iturrate, Luis C.; Prieto, Javier; Kravari, KalliopiToday, the Internet of Things, Big Data and Machine Learning are a regular part of people's daily lives, especially for the elderly or the so-called Silver Economy. There are more and more applications in which collecting and storing information about users (and their context) to produce classifications and predictions allows the optimisation of the services offered, improving the life quality of the citizens. In this sense, leisure cruises represent environments where it is necessary to provide quality services for a reasonable price. This requires understandings the behaviour of users both locally (i.e. each cruise) and globally (i.e. all cruises). In this respect, IoT, Big Data and Machine Learning are presented as ideal technologies for prediction-making and the improvement of the quality of services. However, on ships at sea the transfer rate of the Internet connection is limited. In this sense, Edge Computing allows taking part in the application computing to the Edge of the network, closer to the IoT layer. Data can be filtered and pre-processed in the Edge before it is transmitted to the Cloud, reducing its volume and the associated costs of its computing and storage in the Cloud. Machine Learning algorithms can also be applied to recognise patterns and anomalies on the Edge itself, even if the connectivity with the Cloud is lost. In this paper, we propose the design of a platform which aims to improve the quality of life of the elderly on leisure cruises.
- Effect of Fused Filament Fabrication Processing Parameters on The Mechanical Properties of PLA ComponentsPublication . Marat-Mendes, R.; Guedes, M.; Leite, M.; Baptista, R.This paper studies the influence of Fused Filament Fabrication processing parameters upon mechanical properties and microstructural features of processed PLA parts. The effect of extrusion temperature and raster angle were tested upon two PLA filaments of different trademarks, DoWire and BQ, using a commercial fused deposition extruder. The filling density, layer thickness and velocity were kept constant at 60 %, 0.2 mm and 40 mm/s, respectively. Results allowed to determine fused filament fabrication parameters resulting in increased mechanical performance of manufactured parts. Mechanical performance is higher when material is stored under controlled atmosphere before use, and when material deposition direction is aligned with applied load. Increasing the extrusion temperature also increases performance, by increasing deformation ability of PLA molecules. Obtained results contribute to accumulation of a property database and provide design guidance to the procurement of additive manufacturing products with enhanced mechanical strength.
- Efficient Yield Optimization Method using a Variable K-Means Algorithm for Analog IC SizingPublication . Canelas, A.; Martins, R.; Póvoa, R.; Lourenço, N.; Horta, N.This paper presents the study and implementation of a new efficient yield optimization technique for multi-objective optimization-based automatic analog integrated circuit sizing. The approach uses a commercial electrical simulator and standard process design kit (PDK) models to perform, during the optimization process, the same Monte Carlo (MC) simulations that designers use. The proposed yield estimation technique reduces the number of required MC simulations by using the k-means algorithm, with a variable number of clusters, to select only a handful potential solutions where the MC simulations are performed. Due to the use of a commercial simulator tool and foundry supplied PDK models the developed methodology provides the most accurate and reliable results, and also, the variable k-means algorithm is able to achieve 91% reduction in the total number of the MC simulations required for an optimization, when considering MC simulations for all solutions. Moreover, this new approach presents a 50% increase in speed performance when comparing to a previous yield optimization technique also using k-means and MC simulations.
- Experimental and Numerical Characterization of Stress-Strain Fields on Sandwich Beams, Subjected to 3PB and 4PBPublication . Marat-Mendes, R.; Martins, R.; Reis, L.
- Extended- Range Marine Unmanned Surface Vehicles for Border Surveillance MissionsPublication . Fernandes, J. F. P.; Branco, P. J. Costa; Marat-Mendes, R.; Póvoa, R.; Teodoro, P.; Neves, J.; Marques, H.; Pinheiro, P.; Afonso, P.; Serrano, D.; Assunção, M.This work focuses on the development of extended-range marine unmanned surface vehicles (USV) for border surveillance missions. USVs present many advantages for marine applications due to their energy-saving capabilities and lack of in-board pilot needs. Nevertheless, due to their small scales, USVs often present reduced mission ranges. In order to overcome this handicap, this work proposes the application of innovative energy management strategies to optimize the available energy during one mission. This solution is based on path and speed optimizations, taking into account the most probable weather and sea conditions, to define a mission plan. The proposed energy management optimization is supported by the USV simulation model. This model is calibrated and verified with two experimental tests: one in an indoor swimming pool and the other in an outdoor enclosed harbour. Applying the proposed optimization strategy results in energy savings between 10 and 35.9%, subject to the maximization of mission time. This work is carried out within the international project SEMS4USV, supported by Frontex.