Percorrer por autor "Santos, Nuno"

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    Assessment of a Supervisory Fault-Hiding Scheme in a Classical Guidance, Navigation and Control Setup: the e.Deorbit mission
    (4th International Conference on Control and Fault-Tolerant Systems (SYSTOL), 2019-09-18) Cieslak, Jérôme; Henry, David; Colmenarejo, Pablo; Branco, João; Santos, Nuno; Serra, Pedro; Telaar, Jüergen; Strauch, Hans; Giordano, Alessandro; Stefano, Marco; Ott, Christian; Reiner, Matthias; Jaworski, Jaroslaw; Papadopoulos, Evangelos; Visentin, Gianfranco; Ankersen, Finn; Gil-Fernandez, Jesus; Escola de Comunicação, Arquitetura, Artes e Tecnologias da Informação
    The design of a model-based Fault Tolerant Control (FTC) strategy based on Virtual Actuators (VA) in a built-in Guidance, Navigation and Control (GNC) setup is addressed for the e.Deorbit space mission. This mission, initiated by the European Space Agency (ESA), aims at removing a large defunct satellite from Earth orbit: ENVISAT. The goal of this paper is to promote academic solutions to add fault tolerance capacities against thruster faults without any change or new tuning of the already in-place GNC solution. The validation of the proposed FTC solution is assessed by a simulation campaign based on a high-fidelity nonlinear industrial simulator.
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    Cognitive Stimulation of Elderly Individuals with Instrumental Virtual Reality-Based Activities of Daily Life
    (2019-01-01) Gamito, Pedro; Oliveira, Jorge; Morais, Diogo; Coelho, Cátia; Santos, Nuno; Alves, Catarina; Galamba, Ana; Soeiro, Miguel; Brito, Rodrigo; HEI-LAB (FCT) - Digital Laboratories for Environments and Human Interactions
    As the demographic structure in western societies ages, the prevalence and impact of cognitive decline rises. Thus, new solutions to tackle this problem are required. The use of Information and Communication Tech- nologies (ICT)-based cognitive exercises has emerged in the last few decades, though with inconsistent results. Hence, we conducted a pre-post treatment study to further investigate this approach. We designed a set of virtual reality exercises that mimic activities of daily living by which the patient can train different cognitive domains. Twenty-five participants, ages 65–85, underwent 12 training sessions between the pre-treatment and post-treatment assessments. Significant increases were seen between the two assessments for some of the neuropsychological measures: visual memory, attention, and cognitive flexibility. Results also suggest that participants with lower baseline cognitive performance levels improved most after these sessions.
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    Grabbing attention while reading website pages: the influence of verbal emotional cues in advertising
    (Edições Universitárias Lusófonas, 2011) Ferreira, Paulo Jorge Quaresma; Rita, Paulo; Morais, Diogo; Rosa, Pedro Joel; Oliveira, Jorge; Gamito, Pedro; Santos, Nuno; Soares, Fábio; Sottomayor, Catarina; Escola de Psicologia e Ciências da Vida
    The increasing use of the World Wide Web has promised a huge advertising platform for marketers. Investment in online advertising is growing and is expected to overcome traditional media. However, recent studies have reported that users avoid looking at advertising displayed on the World Wide Web. This study aimed at examining the impact of verbal emotional cues (negative/neutral/positive) to capture attention on website’s advertising areas through an eye tracker system. The results revealed significant statistical differences between fixations to negative, positive words and neutral words. Significant differences between the number of fixations and recognition of the target words were found only for the negative valence words. We conclude that negative emotional words could play a major role on user attention to advertising.
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    Methods and outcomes of the COMRADE project - Design of robust Combined control for robotic spacecraft and manipulator in servicing missions: comparison between between Hinf and nonlinear Lyapunov-based approaches
    (69th International Astronautical Congress (IAC), 2018-10-01) Colmenarejo, Pablo; Branco, João; Santos, Nuno; Serra, Pedro; Telaar, Juergen; Strauch, Hans; Fruhnert, Michael; Giordano, Alessandro; Stefano, Marco; Ott, Christian; Reiner, Matthias; Henry, David; Jaworski, Jaroslaw; Papadopoulos, Evangelos; Visentin, Gianfranco; Ankersen, Finn; Gil-Fernandez, Jesus; Escola de Comunicação, Arquitetura, Artes e Tecnologias da Informação
    Extending life or repairing damaged on-orbit assets is not only a very attractive economic option for satellite operators as it could potentially increase margins for commercial services or increasing delivered value of scientific missions, but it would also help reducing the number of debris objects in space. These types of servicing missions pose technical challenges never faced until now. Of utmost relevance is the autonomous control of several movable devices, whose dynamics are inter-coupled (e.g., spacecraft platform, robotic manipulator, and end-effector), needed to safely and effectively achieve the mission objective. In the frame of ESA-supported COMRADE study, fully combined control (single control system controlling simultaneously all movable devices) is proposed due to its higher improvement potential (propellant saving, performances increase, safety) w.r.t. tele-operation, decoupled and/or collaborative control (the last one characterized by the use of two different control systems for the spacecraft platform and robotic manipulator respectively but, differently to the decoupled version, with information/feedback about what the other control system intends to do). Two independent combined control designs are developed in COMRADE (H∞ and nonlinear Lyapunov-based), and tested. Each of them is applied for both Active Debris Removal (ADR) and servicing/re-fuelling mission scenarios. This paper presents: the processes of scenario analysis and derivation of COMRADE system requirements; a description of the design and setup for a Simulator, which included at its core the selection, prototyping and integration of algorithms for Guidance, Navigation and Control (GNC), Modes Management (AMM) and Failures Detection, Isolation and Recovery (FDIR) (all three together compose the COMRADE system) and the outcomes of the simulation phase of the Verification & Validation process.
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    Model-based fault diagnosis and tolerant control: the ESA’s e.Deorbit mission
    (European Control Conference (ECC19), 2019) Henry, David; Cieslak, Jérôme; Zenteno, J.; Colmenarejo, Pablo; Branco, João; Santos, Nuno; Serra, Pedro; Telaar, Jüergen; Strauch, Hans; Giordano, Alessandro; Ott, Christian; Reiner, Matthias; Jaworski, Jaroslaw; Papadopoulos, Evangelos; Visentin, Gianfranco; Ankersen, Finn; Gil-Fernandez, Jesus; Escola de Comunicação, Arquitetura, Artes e Tecnologias da Informação
    The ESA (European Space Agency) is currently pursuing the development of the e.Deorbit mission that will remove a large defunct satellite from Earth orbit: ENVISAT. To fulfil the mission autonomy requirements, ESA has decided to embed in the GNC (Guidance, Navigation, Control) software, fault tolerance capacities against actuator faults. The aim of this paper is to present the development and validation of a model-based fault diagnosis and tolerant control solution for such faults. The proposed solution is based on a new class of nonlinear unknown input observers, optimal in the L2-gain sense, and a modified version of the nonlinear inverse pseudo control allocation technique. An intensive simulation campaign conducted within a high-fidelity nonlinear industrial simulator, demonstrates the efficiency of the approach.
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    Virtual Reality-Based Cognitive Stimulation to Improve Cognitive Functioning in Community Elderly
    (2020-03) Gamito, Pedro; Oliveira, Jorge; Alves, Catarina; Santos, Nuno; Coelho, Cátia; Brito, Rodrigo; HEI-LAB (FCT) - Digital Laboratories for Environments and Human Interactions
    The advantages of using naturalistic virtual reality (VR) environments based on everyday life tasks for cog- nitive intervention in the elderly are not yet well understood. The literature suggests that the similarity of such exercises with real life activities may improve generalizability by extending the transfer of gains of training to everyday living. This study aimed to investigate the gains associated with this ecologically-oriented virtual reality cognitive stimulation (VR-CS) versus standard cognitive stimulation in the elderly. Forty-three healthy older adults were divided into two groups: an experimental group underwent a VR-based cognitive stimulation and an active control group underwent a paper-and-pencil cognitive stimulation. The outcomes assessed at the pre-treatment and posttreatment assessment consisted in well-established tests for cognitive and executive functioning, depression, subjective well-being, and functionality. The results showed positive outcomes on dimensions of general cognition, executive functioning, attention, and visual memory in the group that un- derwent VR-CS. Improvements in executive functioning in this group was supported by consistent evidence of increases in attention abilities but little evidence of increases in memory abilities. Both effects may have contributed to improvements in general cognition. Further studies are needed to test whether these effects may extend to well-being and functionality in cognitively impaired older adults.