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Neves da Fonseca Cardoso Carreira, Fernando Paulo
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- Complementary filter design with three frequency bands: robot attitude estimationPublication . Carreira, Fernando; Calado, João Manuel Ferreira; Cardeira, Carlos Batista; Oliveira, Paulo Jorge Coelho RamalhoThis paper extents the by now classic sensor fusion complementary filter (CF) design, involving two sensors, to the case where three sensors that provide measurements in different bands are available. This paper shows that the use of classical CF techniques to tackle a generic three sensors fusion problem, based solely on their frequency domain characteristics, leads to a minimal realization, stable, sub-optimal solution, denoted as Complementary Filters3 (CF3). Then, a new approach for the estimation problem at hand is used, based on optimal linear Kalman filtering techniques. Moreover, the solution is shown to preserve the complementary property, i.e. the sum of the three transfer functions of the respective sensors add up to one, both in continuous and discrete time domains. This new class of filters are denoted as Complementary Kalman Filters3 (CKF3). The attitude estimation of a mobile robot is addressed, based on data from a rate gyroscope, a digital compass, and odometry. The experimental results obtained are reported.
- Enhanced PCA-based localization using depth maps with missing dataPublication . Carreira, Fernando; Calado, João Manuel Ferreira; Cardeira, Carlos; Oliveira, PauloIn this paper a new method for self-localization of mobile robots, based on a PCA positioning sensor to operate in unstructured environments, is proposed and experimentally validated. The proposed PCA extension is able to perform the eigenvectors computation from a set of signals corrupted by missing data. The sensor package considered in this work contains a 2D depth sensor pointed upwards to the ceiling, providing depth images with missing data. The positioning sensor obtained is then integrated in a Linear Parameter Varying mobile robot model to obtain a self-localization system, based on linear Kalman filters, with globally stable position error estimates. A study consisting in adding synthetic random corrupted data to the captured depth images revealed that this extended PCA technique is able to reconstruct the signals, with improved accuracy. The self-localization system obtained is assessed in unstructured environments and the methodologies are validated even in the case of varying illumination conditions.
- A gantry robot automatic positioning system using computational visionPublication . Beites, Nuno; Dias, Manuel; Gonçalves Cavaco Mendes, Mário José; Carreira, Fernando; Campos, F.; Calado, João Manuel FerreiraWith the new industrial revolution (industry 4.0) under way, there is a need to automate/digitalize even the simplest processes to keep companies competitive, efficient and secure. This work proposes an automatic and robotic positioning system with position control through the image of video cameras. The objective is to propose this type of automatic system to companies aiming to improve robotic systems operations that are often controlled manually and with associated risks. The developed system was tested in simulation (using Matlab) and in an experimental scale prototype.
- Supervision System 4.0 for a Road Tanker Washing Robot ManipulatorPublication . Vicente, L.; Carreira, Fernando; Campos, Francisco M.; Gonçalves Cavaco Mendes, Mário José; Calado, João Manuel Ferreira; Carvalho, GamboaThe washing of road tankers is currently still a manual process that requires an operator to place the washing head into the tanks. To increase productivity and operator safety, it is essential to implement automated systems with Fault Detection and Isolation (FDI) capabilities. On the other hand, the industry 4.0 paradigm promotes the use of collaborative systems that integrate with the other organization’s processes. Realizing this new vision requires Supervision, Control and Data Acquisition (SCADA) systems with FDI modules that integrate with collaborative systems and promote the digitalization of companies. This paper proposes a SCADA system for a new road tanker washing robot, aimed at integrating all systems and communication networks of the organization and future FDI modules. To this end, this paper proposes a communication architecture based on open protocols and a common database to connect SCADA to the lower and higher levels of automation. Furthermore, this paper describes the various aspects of SCADA system development, from synoptic design to validation. To support the development of the SCADA system, a Digital Twin (DT) of the road tanker washing robot was used, allowing to test and validate its functionality through this virtual prototype. The results show that the proposed SCADA system and underlying information architecture are suitable for supervision of a robotized wash operation and that the use of a Digital Twin facilitates SCADA system design and validation.
- Assessment of influential operational parameters in the mitigation of CO2 emissions in a power plant: case study in PortugalPublication . Balanuta, Vítor; Baptista, Patrícia; Carreira, Fernando; Duarte, Gonçalo; Casaca, Cláudia S. S. L.The European decarbonization goals and requirement for energy independence are mostly relying on intermittent renewable energy sources for electrification. A numerical model was developed to simulate the operation of a steam generator, allowing a study of the potential impacts of retrofitting existing coal-fired power plants to operate with biomass or coal–biomass mixtures on combustion parameters and CO2 emissions. The results obtained using the operational parameters of the Sines power plant indicate that a mixture of 25% coal and 75% pine sawdust allow operation at λ = 1.8, demonstrating that a small amount of coal allows operation near the coal combustion parameters (λ = 1.9). These conditions have the drawback of a reduction of 8.7% in adiabatic flame temperature but a significant reduction of 57.5% in CO2 emissions, considering the biomass as carbon-neutral.
- Finding a short path for mobile robot arm coverage of a point setPublication . Campos, Francisco M.; Carreira, Fernando; Calado, João Manuel FerreiraThis paper introduces the problema of Mobile Robot Arm Covering (MRAC) along with a three-step procedure to solve it. In Mobile Robot Arm Covering one seeks the shortest path of a mobile robot equipped with a manipulator such that the manipulator workspace covers a given set of geometric entities. In this paper we consider the problema of covering a set of points. This is solved by a three-step procedure: the search space is first discretized into a finite set of robot poses; then the resulting combinatorial problem is solved by a memetic algorithm and, finally, the given solution is improved in the continuous space. Two popular discretization schemes developed for the related Close Enough Traveling Salesman Problem (CETSP) are evaluated in the MRAC context. Futhermore, a new memetic algorithm to solve MRAC and CETSP instances is developed. This algorithm overcomes the limitations of the approaches based on General Traveling Salesman Problem (GTSP) solvers, namely, the difficulty in handling large problems and the large computational times required to solve them.
- 2D PCA-Based localization for mobile robots in unstructured environmentsPublication . Carreira, Fernando; Christo, C.; Valerio, D.; Ramalho, M.; Cardeira, C.; Calado, João Manuel Ferreira; Oliveira, P.In this paper a new PCA-based positioning sensor and localization system for mobile robots to operate in unstructured environments (e. g. industry, services, domestic ...) is proposed and experimentally validated. The inexpensive positioning system resorts to principal component analysis (PCA) of images acquired by a video camera installed onboard, looking upwards to the ceiling. This solution has the advantage of avoiding the need of selecting and extracting features. The principal components of the acquired images are compared with previously registered images, stored in a reduced onboard image database, and the position measured is fused with odometry data. The optimal estimates of position and slippage are provided by Kalman filters, with global stable error dynamics. The experimental validation reported in this work focuses on the results of a set of experiments carried out in a real environment, where the robot travels along a lawn-mower trajectory. A small position error estimate with bounded co-variance was always observed, for arbitrarily long experiments, and slippage was estimated accurately in real time.
- Navigation system for mobile robots using PCA-based localization from ceiling depth images: experimental validationPublication . Carreira, Fernando; Calado, João Manuel Ferreira; Cardeira, Carlos; Oliveira, P.This paper aims the experimental validation of a mobile robot navigation system, using self-localization based on principal component analysis (PCA) of ceiling depth images. In this approach, a roadmap based on generalized Voronoi diagram (GVD) is built from an occupancy grid, that is defined in the ceiling mapping to the PCA database. The system resorts to the Dijkstra algorithm to planning paths, using the GVD-based roadmap, from which a set of waypoints are extracted. During the mission, the robot is commanded by a controller based on self-located using only the information provided from ceiling depth images and other on-board sensors. The navigation system ensures that the robot reaches its destination, travelling along safety trajectories, while computing its pose with global stable estimates, from Kalman filters (KF). The navigation is achieved without the need to structure the environment, searching by specific features, and to linearize the model. The results are experimentally validated in an indoor environment, using a differential-drive mobile robot.
- A photorealistic digital twin for a tank truck washing robotic systemPublication . Vicente, Luís; Lomelino, Pedro; Carreira, Fernando; Campos, Francisco M.; Gonçalves Cavaco Mendes, Mário José; Calado, J. M. F.In the current industrial context, the adoption of a digital twin (DT) has proven to be an appropriate tool to optimize the entire lifecycle of a system. This vision includes the adoption of a DT, in the collaborative network of organizations from the virtual modeling of a system, through its control, operation, namely simulation, implementation, and monitoring/supervision. To take full advantage of DTs, it is essential that they are as photorealistic as possible, allowing all kinds of simulations to be carried out, for example testing vision algorithms. In this context, this paper presents the development of a DT that is integrated as a collaborative system to monitor all phases of the life cycle of a robot destined to wash tank truck. The Unreal Engine 4 software was used to develop a DT and the communication architecture was designed, using the standard OPC UA protocol.
- A complete frontier-based exploration method for Pose-SLAMPublication . Marques, Miguel; Carreira, Fernando; Calado, João Manuel FerreiraIn this paper we propose a complete frontier-based exploration method for Pose SLAM. The goal of current frontierbased exploration methods is to eliminate all frontiers in the environment map. This approach, however, does not meet the requirements of Pose SLAM mapping: besides arriving at a frontier free map, there is the need to close the loops in the environment. In fact, loop closing is instrumental to Pose SLAM, since the major corrections to the map result from adding place revisiting constraints. The exploration method we propose is said to be complete in the sense that all loops are guaranteed to be closed. In this paper, we also describe a hybrid map that supports our exploration scheme and detail all the mechanisms required to maintain it during exploration. The validity of the approach is demonstrated on a widely used dataset.