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Publicações

2024

Assessment of Multiple Fiducial Marker Trackers on Hololens 2

Autores
Costa, GM; Petry, MR; Martins, JG; Moreira, APGM;

Publicação
IEEE ACCESS

Abstract
Fiducial markers play a fundamental role in various fields in which precise localization and tracking are paramount. In Augmented Reality, they provide a known reference point in the physical world so that AR systems can accurately identify, track, and overlay virtual objects. This accuracy is essential for creating a seamless and immersive AR experience, particularly when prompted to cope with the sub-millimeter requirements of medical and industrial applications. This research article presents a comparative analysis of four fiducial marker tracking algorithms, aiming to assess and benchmark their accuracy and precision. The proposed methodology compares the pose estimated by four algorithms running on Hololens 2 with those provided by a highly accurate ground truth system. Each fiducial marker was positioned in 25 sampling points with different distances and orientations. The proposed evaluation method is not influenced by human error, relying only on a high-frequency and accurate motion tracking system as ground truth. This research shows that it is possible to track the fiducial markers with translation and rotation errors as low as 1.36 mm and 0.015 degrees using ArUco and Vuforia, respectively.

2024

Energy Efficiency Analysis of Differential and Omnidirectional Robotic Platforms: A Comparative Study

Autores
Chellal, AA; Braun, J; Bonzatto, L Jr; Faria, M; Kalbermatter, RB; Gonçalves, J; Costa, P; Lima, J;

Publicação
SYNERGETIC COOPERATION BETWEEN ROBOTS AND HUMANS, VOL 1, CLAWAR 2023

Abstract
As robots have limited power sources. Energy optimization is essential to ensure an extension for their operating periods without needing to be recharged, thus maximizing their uptime and minimizing their running costs. This paper compares the energy consumption of different mobile robotic platforms, including differential, omnidirectional 3-wheel, omnidirectional 4-wheel, and Mecanum platforms. The comparison is based on the RobotAtFactory 4.0 competition that typically takes place during the Portuguese Robotics Open. The energy consumption from the batteries for each platform is recorded and compared. The experiments were conducted in a validated simulation environment with dynamic and friction models to ensure that the platforms operated at similar speeds and accelerations and through a 5200 mAh battery simulation. Overall, this study provides valuable information on the energy consumption of different mobile robotic platforms. Among other findings, differential robots are the most energy-efficient robots, while 4-wheel omnidirectional robots may offer a good balance between energy efficiency and maneuverability.

2024

Fourier (Common-Tone) Phase Spaces are in Tune with Variational Autoencoders' Latent Space

Autores
Carvalho, N; Bernardes, G;

Publicação
MATHEMATICS AND COMPUTATION IN MUSIC, MCM 2024

Abstract
Expanding upon the potential of generative machine learning to create atemporal latent space representations of musical-theoretical and cognitive interest, we delve into their explainability by formulating and testing hypotheses on their alignment with DFT phase spaces from {0, 1}(12) pitch classes and {0, 1}(128) pitch distributions - capturing common-tone tonal functional harmony and parsimonious voice-leading principles, respectively. We use 371 J.S. Bach chorales as a benchmark to train a Variational Autoencoder on a representative piano roll encoding. The Spearman rank correlation between the latent space and the two before-mentioned DFT phase spaces exhibits a robust rank association of approximately .65 +/- .05 for pitch classes and .61 +/- .05 for pitch distributions, denoting an effective preservation of harmonic functional clusters per region and parsimonious voice-leading. Furthermore, our analysis prompts essential inquiries about the stylistic characteristics inferred from the rank deviations to the DFT phase space and the balance between the two DFT phase spaces.

2024

Hybrid renewable energy system optimisation for application in the winemaking sector

Autores
Teixeira, R; Cerveira, A; Silva, A; Baptista, J;

Publicação
2024 IEEE 22nd Mediterranean Electrotechnical Conference, MELECON 2024

Abstract
The objective of achieving carbon neutrality by 2050 requires the various sectors of the economy to actively participate in the decarbonisation of all their activities, from production to consumption and product distribution. The vineyard and wine production sector is no exception to this goal. This paper aims to evaluate the feasibility and efficiency that hybrid energy systems based on renewable energy sources, solar photovoltaic (PV) and wind, can contribute to energy efficiency in certain activities related to wine production. In this sense, this study presents results based on linear programming optimisation models, which show how effective they are in minimising the use of energy from the power grid. The results show that renewable hybrid energy systems based on PV and wind are an effective solution for achieving carbon neutrality in some agricultural sectors, particularly winemaking sector. Besides being able to minimise the energy bought from the grid, the hybrid renewable energy system (HRES) is almost self-sufficient, being able to produce 340,232 kWh over 25 years. © 2024 IEEE.

2024

The Effect of the TiO2 Anodization Layer in Pedicle Screw Conductivity: An Analytical, Numerical, and Experimental Approach

Autores
Fonseca, P; Goethel, MF; Vilas-Boas, JP; Gutierres, M; Correia, MV;

Publicação
BIOENGINEERING-BASEL

Abstract
The electrical stimulation of pedicle screws is a technique used to ensure its correct placement within the vertebrae pedicle. Several authors have studied these screws' electrical properties with the objective of understanding if they are a potential source of false negatives. As titanium screws are anodized with different thicknesses of a high electrical resistance oxide (TiO2), this study investigated, using analytical, numerical, and experimental methods, how its thickness may affect pedicle screw's resistance and conductivity. Analytical results have demonstrated that the thickness of the TiO2 layer does result in a significant radial resistance increase (44.21 m Omega/nm, for & Oslash; 4.5 mm), and a decrease of conductivity with layers thicker than 150 nm. The numerical approach denotes that the geometry of the screw further results in a decrease in the pedicle screw conductivity, especially after 125 nm. Additionally, the experimental results demonstrate that there is indeed an effective decrease in conductivity with an increase in the TiO2 layer thickness, which is also reflected in the screw's total resistance. While the magnitude of the resistance associated with each TiO2 layer thickness may not be enough to compromise the ability to use anodized pedicle screws with a high-voltage electrical stimulator, pedicle screws should be the subject of more frequent electrical characterisation studies.

2024

Towards truly sustainable IoT systems: the SUPERIOT project

Autores
Katz, M; Paso, T; Mikhaylov, K; Pessoa, L; Fontes, H; Hakola, L; Leppaeniemi, J; Carlos, E; Dolmans, G; Rufo, J; Drzewiecki, M; Sallouha, H; Napier, B; Branquinho, A; Eder, K;

Publicação
JOURNAL OF PHYSICS-PHOTONICS

Abstract
This paper provides an overview of the SUPERIOT project, an EU SNS JU (Smart Networks and Services Joint Undertaking) initiative focused on developing truly sustainable IoT systems. The SUPERIOT concept is based on a unique holistic approach to sustainability, proactively developing sustainable solutions considering the design, implementation, usage and disposal/reuse stages. The concept exploits radio and optical technologies to provide dual-mode wireless connectivity and dual-mode energy harvesting as well as dual-mode IoT node positioning. The implementation of the IoT nodes or devices will maximize the use of sustainable printed electronics technologies, including printed components, conductive inks and substrates. The paper describes the SUPERIOT concept, covering the key technical approaches to be used, promising scenarios and applications, project goals and demonstrators which will be developed to the proof-of-concept stage. In addition, the paper briefly discusses some important visions on how this technology may be further developed in the future.

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