An Indirect Adaptive Control Approach to Image Based Visual Servoing for Translational Trajectory Tracking

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Dynamic Smooth Sliding Control Applied to UAV Trajectory Tracking

This paper proposes a sliding mode controller with smooth control effort for a class of nonlinear plants. The proposed controller is created by allowing some constant parameters of the earlier smooth sliding control (SSC) to vary as a function of the output tracking error, improving the control chattering alleviation in practical implementations. Furthermore, during the sliding mode, the new scheme can synthesize a range of controllers, such as fixed gain PI controllers and approximations of the standard Super-Twisting Algorithm (STA), as well as, the variable gain Super-Twisting Algorithm (VGSTA). A complete closed-loop stability analysis is provided. In addition, realistic simulation results with an unmanned aerial vehicle (UAV) model, incorporating aerodynamic effects and internal closed-loop controllers, are obtained and validated via experiments with a commercial hexacopter

Adaptive Passivity-based Hybrid Pose/Force Control for Uncertain Robots

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Multi-DoF Time Domain Passivity Approach Based Drift Compensation for Telemanipulation

When, in addition to stability, position synchronization is also desired in bilateral teleoperation, Time Domain Passivity Approach (TDPA) alone might not be able to fulfill the desired objective. This is due to an undesired effect caused by admittance type passivity controllers, namely position drift. Previous works focused on developing TDPA-based drift compensation methods to solve this issue. It was shown that, in addition to reducing drift, one of the proposed methods was able to keep the force signals within their normal range, guaranteeing the safety of the task. However, no multi-DoF treatment of those approaches has been addressed. In that scope, this paper focuses on providing an extension of previous TDPA-based approaches to multi-DoF Cartesian-space teleoperation. An analysis of the convergence properties of the presented method is also provided. In addition, its applicability to multi-DoF devices is shown through hardware experiments and numerical simulation with round-trip time delays up to 700 ms.Comment: 2019 19th International Conference on Advanced Robotics (ICAR

Quaternary refugia and secondary contact in the southern boundary of the Brazilian subregion: comparative phylogeography of freshwater fish

Freshwater fish are an ideal model to illustrate how climate-tectonic changes affect the distribution of genetic variation. Freshwater bodies are extensively affected by environmental changes, with streams even changing their courses in the most extreme cases. Fortunately, this situation is reflected in the genetic composition of populations and may currently be inferred from the study of mitochondrial DNA molecular markers. Here we analyze and compare the phylogeographic patterns of the species Corydoras paleatus and Jenynsia multidentata at the southern limit of the Brazilian subregion. These basins are isolated in the current hydrogeographic pattern due to geologic and paleoclimatic changes. Our results support a concurrent pattern for both species. Some lineages have persisted in the area under adverse climate conditions, possibly in environmental refuges, while other lineages may have colonized the area later by means of paleodrainage connections. In addition, the presence of independent, greatly diverging lineages, even within the same watercourses, suggests secondary contact between these lineages. This work represents a first approach to understand how geologic and paleoclimatic changes have affected the distribution of genetic variation in the Southern Pampean AreaFacultad de Ciencias Naturales y MuseoComisión de Investigaciones Científicas de la provincia de Buenos AiresCentro Regional de Estudios GenómicosConsejo Nacional de Investigaciones Científicas y Técnica

Quaternary refugia and secondary contact in the southern boundary of the Brazilian subregion: comparative phylogeography of freshwater fish

Freshwater fish are an ideal model to illustrate how climate-tectonic changes affect the distribution of genetic variation. Freshwater bodies are extensively affected by environmental changes, with streams even changing their courses in the most extreme cases. Fortunately, this situation is reflected in the genetic composition of populations and may currently be inferred from the study of mitochondrial DNA molecular markers. Here we analyze and compare the phylogeographic patterns of the species Corydoras paleatus and Jenynsia multidentata at the southern limit of the Brazilian subregion. These basins are isolated in the current hydrogeographic pattern due to geologic and paleoclimatic changes. Our results support a concurrent pattern for both species. Some lineages have persisted in the area under adverse climate conditions, possibly in environmental refuges, while other lineages may have colonized the area later by means of paleodrainage connections. In addition, the presence of independent, greatly diverging lineages, even within the same watercourses, suggests secondary contact between these lineages. This work represents a first approach to understand how geologic and paleoclimatic changes have affected the distribution of genetic variation in the Southern Pampean AreaFacultad de Ciencias Naturales y MuseoComisión de Investigaciones Científicas de la provincia de Buenos AiresCentro Regional de Estudios GenómicosConsejo Nacional de Investigaciones Científicas y Técnica

Comparison of machine learning algorithms for wildland-urban interface fuelbreak planning integrating ALS and UAV-Borne LiDAR data and multispectral images

Producción CientíficaControlling vegetation fuels around human settlements is a crucial strategy for reducing fire severity in forests, buildings and infrastructure, as well as protecting human lives. Each country has its own regulations in this respect, but they all have in common that by reducing fuel load, we in turn reduce the intensity and severity of the fire. The use of Unmanned Aerial Vehicles (UAV)-acquired data combined with other passive and active remote sensing data has the greatest performance to planning Wildland-Urban Interface (WUI) fuelbreak through machine learning algorithms. Nine remote sensing data sources (active and passive) and four supervised classification algorithms (Random Forest, Linear and Radial Support Vector Machine and Artificial Neural Networks) were tested to classify five fuel-area types. We used very high-density Light Detection and Ranging (LiDAR) data acquired by UAV (154 returns·m−2 and ortho-mosaic of 5-cm pixel), multispectral data from the satellites Pleiades-1B and Sentinel-2, and low-density LiDAR data acquired by Airborne Laser Scanning (ALS) (0.5 returns·m−2, ortho-mosaic of 25 cm pixels). Through the Variable Selection Using Random Forest (VSURF) procedure, a pre-selection of final variables was carried out to train the model. The four algorithms were compared, and it was concluded that the differences among them in overall accuracy (OA) on training datasets were negligible. Although the highest accuracy in the training step was obtained in SVML (OA=94.46%) and in testing in ANN (OA=91.91%), Random Forest was considered to be the most reliable algorithm, since it produced more consistent predictions due to the smaller differences between training and testing performance. Using a combination of Sentinel-2 and the two LiDAR data (UAV and ALS), Random Forest obtained an OA of 90.66% in training and of 91.80% in testing datasets. The differences in accuracy between the data sources used are much greater than between algorithms. LiDAR growth metrics calculated using point clouds in different dates and multispectral information from different seasons of the year are the most important variables in the classification. Our results support the essential role of UAVs in fuelbreak planning and management and thus, in the prevention of forest fires.Ministerio de Economía, Industria y Competitividad (DI-16-08446; DI-17-09626; PTQ-16-08411; PTQ- 16-08633)European Commission through the project ‘MySustainableForest’ (H2020-EO-2017; 776045

Control and Obstacle Collision Avoidance Method applied to Human-robot Interaction

In this work, we present a control and obstacle collision avoidance method for redundant robot manipulators operating in partially structured environments in the presence of humans. The control algorithm is based on the concept of artificial potential fields and it uses the pseudo-inverse of the Jacobian matrix with a weighting factor for the mechanical joint limits, taking advantage of the robot redundancy for the purpose of obstacle avoidance and control goal achievement. The detection algorithm uses a depth sensor based on the structured light to obtain a 2-1/2-D description of the surroundings from a point cloud. Repulsive fields are created around the detected obstacles, allowing for the robot to perform the task of interest without collisions. A filtering methodology based on geometric elements is presented to filter the RGB-D scene captured by the depth sensor, eliminating the robot body and the obstacles located outside its workspace. Experimental results, obtained with a Motoman DIA10 robot and a Microsoft KinectTM, illustrate the feasibility of the proposed scheme

Aplicação de diodos emissores de luz em ambientes hiperbáricos

Em 06/12/2016: Manutenção do Indeferimento. Em 09/08/2016: Indeferimento. Indeferido o pedido por não atender aos requisitos legais, conforme parecer técnico.Não concedidaA inovação ora proposta refere-se à aplicação do diodo emissor de luz, doravante denominado LED (Light-Emitting Diode), em ambientes hiperbáricos secos ou ambientes hiperbáricos molhados. Nesses ambientes o LED pode ser aplicado para iluminar, sinalizar ou como parte integrante de mostradores numéricos de caracteres ou gráficos. Sendo também proposta a aplicação dos LEDs em ambientes hiperbáricos sem estarem protegidos por vasos de pressão. Os LEDs podem ficar em contato direto com o fluido do ambiente líquido ou gasoso, ou protegidos do meio ambiente por um recipiente transparente ou translúcido, fino e leve

Characteristics and Evolution of sill-driven off-axis hydrothermalism in Guaymas Basin – the Ringvent site

The Guaymas Basin spreading center, at 2000 m depth in the Gulf of California, is overlain by a thick sedimentary cover. Across the basin, localized temperature anomalies, with active methane venting and seep fauna exist in response to magma emplacement into sediments. These sites evolve over thousands of years as magma freezes into doleritic sills and the system cools. Although several cool sites resembling cold seeps have been characterized, the hydrothermally active stage of an off-axis site was lacking good examples. Here, we present a multidisciplinary characterization of Ringvent, an ~1 km wide circular mound where hydrothermal activity persists ~28 km northwest of the spreading center. Ringvent provides a new type of intermediate-stage hydrothermal system where off-axis hydrothermal activity has attenuated since its formation, but remains evident in thermal anomalies, hydrothermal biota coexisting with seep fauna, and porewater biogeochemical signatures indicative of hydrothermal circulation. Due to their broad potential distribution, small size and limited life span, such sites are hard to find and characterize, but they provide critical missing links to understand the complex evolution of hydrothermal systems