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Publicações

2018

Torque controlled biped model through a bio-inspired controller using adaptive learning

Autores
Ferreira, C; Cunha, T; Santos, CP; Reis, LP;

Publicação
2018 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS (IROS)

Abstract
Biped robots have not achieved the efficient and harmonious locomotion of the human beings, capable of walking and running on unstructured terrains, with obstacles, holes and slopes. With this in mind, researchers started the development of biomimetic solutions to control the locomotion of biped models. This work presents a new solution of motion control of bipedal robots with adaptable stiffness, by exploring effects of joint stiffness in modulating walking behavior. Further, torque adjustment is achieved through a biomimetic controller that mimics and adjusts the natural dynamics of the robot to the environment. Specifically, the torque adjustment is made using AFOs (adaptive frequency oscillator) to generate the correct equilibrium positions that will be applied to the impedance control that computes the torque of each joint. Results show that the biped model is capable of walking in several types of terrain, including flat terrain, ramps, stairs and flat terrain with obstacles.

2018

Evaluation of the Impact of Shifting Demand from Peak to Adjacent Hours in the Social Welfare Function of the Iberian Electricity Market, MIBEL

Autores
Pinto, PT; Saraiva, JT;

Publicação
2018 15TH INTERNATIONAL CONFERENCE ON THE EUROPEAN ENERGY MARKET (EEM)

Abstract
This paper reports the main results obtained by the first author in the preparation of his MSc Thesis. The motivation for this work resulted from the intention announced by the Portuguese Regulatory Agency for the Energy Services to introduce dynamic tariffs as a way to induce a change of the behavior of some consumers in terms of moving some demand from peak periods to the adjacent hours. This is reported to lead to loss reductions, postponement of grid investments and generation cost reductions. In the case of Portugal, given the participation in the common market with Spain, generation costs are not publicly available so that it was investigated how the Social Welfare Function, SWF, that is maximized by the market operator would change given these demand transfers. The simulations were done using real market data for 2016 and the results suggest that the advantages are unclear since the SWF would be almost unchanged or slightly reduced.

2018

Temperature independent refractive index measurement using a fiber Bragg grating on abrupt tapered tip

Autores
Gomes, AD; Silveira, B; Warren Smith, SC; Becker, M; Rothhardt, M; Frazao, O;

Publicação
OPTICS AND LASER TECHNOLOGY

Abstract
A fiber Bragg grating was inscribed in an abrupt fiber taper using a femtosecond laser and phase-mask interferometer. The abrupt taper transition allows to excite a broad range of guided modes with different effective refractive indices that are reflected at different wavelengths according to Bragg's law. The multimode-Bragg reflection expands over 30 nm in the telecom-C-band. This corresponds to a mode field overlap of up to 30% outside of the fiber, making the device suitable for evanescent field sensing. Refractive index and temperature measurements are performed for different reflection peaks. Temperature independent refractive index measurements are achieved by considering the difference between the wavelength shifts of two measured reflection peaks. A minimum refractive index sensitivity of 16 +/- 1 nm/RlU was obtained in a low refractive index regime (1.3475-1.3720) with low influence of temperature (-0.32 0.06 pm/degrees C). The cross sensitivity for this structure is 2.0 x 10(-5) RlU/degrees C.. The potential for simultaneous measurement of refractive index and temperature is also studied.

2018

Variações sobre espaço #6

Autores
Lopes, Filipe; Bernardes, Gilberto; Cardoso, Clara;

Publicação
4th International Conference on Live Interfaces: Inspiration, Performance, Emancipation

Abstract
We present Variações sobre Espaço #6, a mixed media work for saxophone and electronics that intersects music, digital technologies and architecture. The creative impetus supporting this composition is grounded in the interchange of the following two concepts: 1) the phenomenological exploration of the aural architecture (Blesse & Salter 2007) particularly the reverberation as a sonic effect (Augoyard & Torgue 2005) through music performance and 2) the real time sound analysis of both the performance and the reverberation (i.e. impulse responses) intervallic content — which ultimately leads to a generic control over consonance/dissonance (C/D). Their conceptual and morphological nature can be understood as sonic improvisations where the interaction of sound producing bodies (i.e. the saxophone) with the real (e.g. performance space) and the imaginary (i.e. computer) acoustic response of a space results in formal elements mirroring their physical surroundings.

2018

Assessing Containerized REST Services Performance in the Presence of Operator Faults

Autores
Cunha, M; Laranjeiro, N;

Publicação
2018 14TH EUROPEAN DEPENDABLE COMPUTING CONFERENCE (EDCC 2018)

Abstract
Service applications are increasingly being deployed in virtualized environments, such as virtual machines (VMs) as a means to provide elasticity and to allow fast recovery from failures. The recent trend is now to deploy applications in containers (e.g., Docker or RKT containers), which allow, among many other benefits, to further reduce recovery time, since containers are much more lightweight than VMs. Although several performance benchmarks exist for web services (e.g., TPC-App and SPEC SPECjEnterprise2010) or even virtualized environments (e.g., SPEC Cloud IaaS 2016, TPCx-V), understanding the behavior of containerized services in the presence of faults has been generally disregarded. This paper proposes an experimental approach for evaluating the performance of containerized services in presence of operator faults. The approach is based on the injection of a simple set of operator faults targeting the containers and middleware. Results show noticeable differences regarding the impact of operator faults in Docker and RKT, with the latter one allowing for faster recovery, despite showing the lowest throughput.

2018

Data Mining for Prosumers Aggregation considering the Self-Generation

Autores
Ribeiro, C; Pinto, T; Vale, Z; Baptista, J;

Publicação
DISTRIBUTED COMPUTING AND ARTIFICIAL INTELLIGENCE

Abstract
Several challenges arrive with electrical power restructuring, liberalized electricity markets emerge, aiming to improve the system's efficiency while offering new economic solutions. Privatization and liberalization of previously nationally owned systems are examples of the transformations that have been applied. Microgrids and smart grids emerge and new business models able to cope with new opportunities start being developed. New types of players appear, allowing aggregating a diversity of entities, e. g. generation, storage, electric vehicles, and consumers, Virtual Power Players (VPPs) are a new type of player that allows aggregating a diversity of players to facilitate their participation in the electricity markets. A major task of VPPs is the remuneration of generation and services (maintenance, market operation costs and energy reserves), as well as charging energy consumption. The paper proposes a normalization method that supports a clustering methodology for the remuneration and tariffs definition. This model uses a clustering algorithm, applied on normalized load values, the value of the micro production, generated in the bus associated to the same load, was subtracted from the value of the consumption of that load. This calculation is performed in a real smart grid on buses with associated micro production. This allows the creation of sub-groups of data according to their correlations. The clustering process is evaluated so that the number of data sub-groups that brings the most added value for the decision making process is found, according to players characteristics.

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