António Paulo Coimbra

Prof. Dr. António Paulo Coimbra

orcid

Research Focus & Metrics

Academic Career Length

33Years (1994-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 May 2017 in Energy Economics
Verified
Journal Article
Closed access
DNDaywes Pinheiro Neto
Daywes Pinheiro Neto
EDElder Geraldo Domingues
Elder Geraldo Domingues
ACAntónio Paulo Coimbra
António Paulo Coimbra
Anibal T. de AlmeidaAnibal T. de Almeida
Anibal T. de Almeida
AAAylton José Alves
Aylton José Alves
WCWesley Pacheco Calixto
Wesley Pacheco Calixto

19 May 2009 in IEEE Transactions on Instrumentation and Measurement
Verified
Journal Article
Closed access
João FerreiraJoão Ferreira
João Ferreira
MCManuel Crisóstomo
Manuel Crisóstomo
ACAntónio Paulo Coimbra
António Paulo Coimbra
This paper analyzes human motion, more specifically the human gait in the sagittal plane. A video camera is used to acquire images of a walking person, fitted with a set of white light-emitting diodes (LEDs). The acquired trajectories of the light points are then used to specify joint trajectories in a biped robot. To analyze the stability of the human gait, a system was also developed to acquire the center of pressure (CoP). This system uses eight force sensors, four under each foot. The influence of the human torso angle on the CoP position during walking was confirmed. Some experiments were carried out on a biped robot, and the results show that the acquired human gait can be used in a biped robot, after scale conversion.

2 October 2009 in IEEE Transactions on Neural Networks
Verified
Journal Article
Closed access
João FerreiraJoão Ferreira
João Ferreira
MCManuel Crisóstomo
Manuel Crisóstomo
ACAntónio Paulo Coimbra
António Paulo Coimbra
The real-time balance control of an eight-link biped robot using a zero moment point (ZMP) dynamic model is difficult due to the processing time of the corresponding equations. To overcome this limitation, two alternative intelligent computing control techniques were compared: one based on support vector regression (SVR) and another based on a first-order Takagi-Sugeno-Kang (TSK)-type neural-fuzzy (NF) network. Both methods use the ZMP error and its variation as inputs and the output is the correction of the robot's torso necessary for its sagittal balance. The SVR and the NF were trained based on simulation data and their performance was verified with a real biped robot. Two performance indexes are proposed to evaluate and compare the online performance of the two control methods. The ZMP is calculated by reading four force sensors placed under each robot's foot. The gait implemented in this biped is similar to a human gait that was acquired and adapted to the robot's size. Some experiments are presented and the results show that the implemented gait combined either with the SVR controller or with the TSK NF network controller can be used to control this biped robot. The SVR and the NF controllers exhibit similar stability, but the SVR controller runs about 50 times faster.

14 February 2022 in Energies
Verified
Journal Article
Open access
PDF file
Alexandre Matias CorreiaAlexandre Matias Correia
Alexandre Matias Correia
LFLuís Ferreira
Luís Ferreira
ACAntónio Paulo Coimbra
António Paulo Coimbra
Pedro MouraPedro Moura
Pedro Moura
Anibal T. de AlmeidaAnibal T. de Almeida
Anibal T. de Almeida
Achieving nearly zero-energy buildings (nZEB) is one of the main objectives defined by the European Union for achieving carbon neutrality in buildings. nZEBs are heavily reliant on distributed renewable generation energy sources, which create new challenges associated with their inherent intermittency. To achieve nZEB levels, demand management plays an essential role to balance supply and demand. Since up to two-thirds of the total consumed energy in buildings is dispended for Heating, Ventilation and Air Conditioning (HVAC) operations, intelligent control of HVAC loads is of utmost importance. The present work aims to offer a solution to improve a building microgrids’ flexibility by shifting thermal loads and taking advantage of room thermal inertia. Innovation is present in using the internet of things to link several decentralized local microcontrollers with the microgrid and in the applicability of different control algorithms, such as the pre-emptive heating/cooling of a room. The developed solution relies on smart thermostats, which can be integrated into a building management system, or in a microgrid, and are capable of fulfilling the occupants’ need for comfort while complementing the building with needed power flexibility. The equipment is capable of controlling several HVAC systems to guarantee thermal and air quality comfort, as well as coordinate with a building/microgrid operator to reduce energy costs by shifting thermal loads and enacting demand control strategies. The smart thermostat uses an algorithm to calculate room inertia and to pre-emptively heat/cool a room to the desired temperature, avoiding peak hours, taking advantage of variable tariffs for electricity, or periods of solar generation surplus. The smart thermostat was integrated into a university campus microgrid and tested in live classrooms. Since the work was developed during the COVID-19 pandemic, special attention was given to the air quality features. Results show that smart HVAC control is a viable way to provide occupant comfort, as well as contribute to the integration of renewable generation and increase energy efficiency in buildings and microgrids.

12 June 2012 in IEEE Transactions on Power Delivery
Verified
Journal Article
Closed access
WCWesley Pacheco Calixto
Wesley Pacheco Calixto
ACAntónio Paulo Coimbra
António Paulo Coimbra
BABernardo Alvarenga
Bernardo Alvarenga
Jose MolinJose Molin
Jose Molin
Alexandre CardosoAlexandre Cardoso
Alexandre Cardoso
LNLuciano Martins Neto
Luciano Martins Neto
The purpose of this paper is to present an innovative methodology for 3-D soil stratification based on geoelectrical prospection. This methodology is useful in optimal substation grounding system designs by providing an accurate 3-D soil resistivity model. In the present methodology, the area being studied is subdivided into squared subareas and a recently developed geoelectrical prospection method based on the Wenner's method and on a genetic algorithm is applied to each subarea's edge. For each subarea, the soil stratification result consists of the number of layers and of its electrical resistivities and thicknesses. A global 3-D soil stratification solution is then obtained from these data. Results obtained with this new method are presented and discussed.

9 May 2023 in Applied Sciences
Verified
Journal Article
Open access
PDF file
JSJosé Santos
José Santos
Nuno PeixinhoNuno Peixinho
Nuno Peixinho
TBTeresa Barata
Teresa Barata
CPCarlos Pereira
Carlos Pereira
ACAntónio Paulo Coimbra
António Paulo Coimbra
mateus mendesmateus mendes
mateus mendes
Solar activity has been subject to increasingly more research in the last decades. Its influence on life on Earth is now better understood. Solar winds impact the earth’s magnetic field and atmosphere. They can disrupt satellite communication and navigation tools and even electrical power grids and several other infrastructure crucial for our technology-based society. Coronal mass ejections (CMEs), solar energetic particles, and flares are the main causes of problems that affect the systems mentioned. It is possible to predict some of those by monitoring the sun and analyzing the images obtained in different spectra, thus identifying solar phenomena related to its activity, such as filaments, pores, and sunspots. Several studies have already been carried out on the subject of automation of the mentioned analysis, most of which use neural networks and other machine learning approaches. In this work, we develop a method for sunspot detection based on the YOLOv5 network, applying it to a dataset of images from the Geophysical and Astronomical Observatory of the University of Coimbra (OGAUC), which has one of the oldest and more complete datasets of sun images in the world. Our method reaches mAP@.5 over 90% with YOLOv5s, which is higher than other methods previously applied for the same dataset. This shows that CNN models can be used in spectroheliographs for detecting and tracking sunspots.