Browsing by Author "Costa, Pedro"
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- A* search algorithm optimization path planning in mobile robots scenariosPublication . Lima, José; Costa, Pedro; Costa, Paulo Gomes da; Eckert, Lucas; Piardi, Luis; Moreira, António Paulo G. M.; Nakano, Alberto YoshiroPath planning for mobile robotics in unknown environments or with moving obstacles requires re-planning paths based on information gathered from the surroundings. Moving obstacles and real time constraints require fast computing to navigate and make decisions in a mobile robot. This paper addresses an optimization approach to compute, with real time constraints, the optimal path for a mobile robot based on a dynamically simplified A* search algorithm with a commitment on the available time.
- An optimization approach for the inverse kinematics of a highly redundant robotPublication . Costa, Paulo Gomes da; Lima, José; Pereira, Ana I.; Costa, Pedro; Pinto, AndryThis paper describes a robot with 12 degrees of freedom for pick-and-place operations using bricks. In addition, an optimization approach is proposed, which determines the state of each joint (that establishes the pose for the robot) based on the target position while minimizing the effort of the servomotors avoiding the inverse kinematics problem, which is a hard task for a 12 DOF robot manipulator. Therefore, it is a multi-objective optimization problem that will be solved using two optimization methods: the Stretched Simulated Annealing method and the NSGA II method. The experiments conducted in a simulation environment prove that the proposed approach is able to determine a solution for the inverse kinematics problem. A real robot formed by several servomotors and a gripper is also presented in this research for validating the solutions.
- Ball detection for robotic soccer: a real-time RGB-D approachPublication . Morais, André; Costa, Pedro; Lima, JoséThe robotic football competition has encouraged the participants to develop new ways of solving different problems in order to succeed in the competition. This article shows a different approach to the ball detection and recognition by the robot using a Kinect System. It has enhanced the capabilities of the depth camera in detecting and recognizing the ball during the football match. This is important because it is possible to avoid the noise that the RGB cameras are subject to for example lighting issues.
- Cable robot for non-standard architecture and construction: A dynamic positioning systemPublication . Moreira, Eduardo; Pinto, Andry; Costa, Paulo Gomes da; Moreira, António Paulo G. M.; Veiga, Germano; Lima, José; Sousa, Jose Pedro; Costa, PedroIn the past few years, cable-driven robots have received some attention by the scientific community and the industry. They have special characteristics that made them very reliable to operate with the level of safeness that is required by different environments, such as, handling of hazardous materials in construction sites. This paper presents a cable-driven robot called SPIDERobot, that was developed for automated construction of architectural projects. This robot has a rotating claw and it is controlled by a set of 4 cables that allow 4 degrees of freedom. In addition to the robot, this paper introduces a Dynamic Control System (DCS) that controls the positioning of the robot and assures that the length of cables is always within a safe value. Results show that traditional force-feasible approaches are more influenced by the pulling forces or the geometric arrangement of all cables and their positioning is significantly less accurate than the DCS. Therefore, the architecture of the SPIDERobot is designed to enable an easily scaling up of the solution to higher dimensions for operating in realistic environments.
- A cable-driven robot for architectural constructions: a visual-guided approach for motion control and path-planningPublication . Pinto, Andry; Moreira, Eduardo; Lima, José; Sousa, José Pedro; Costa, PedroCable-driven robots have received some attention by the scientific community and, recently, by the industry because they can transport hazardous materials with a high level of safeness which is often required by construction sites. In this context, this research presents an extension of a cable-driven robot called SPIDERobot, that was developed for automated construction of architectural projects. The proposed robot is formed by a rotating claw and a set of four cables, enabling four degrees of freedom. In addition, this paper proposes a new Vision-Guided Path-Planning System (V-GPP) that provides a visual interpretation of the scene: the position of the robot, the target and obstacles location; and optimizes the trajectory of the robot. Moreover, it determines a collision-free trajectory in 3D that takes into account the obstacles and the interaction of the cables with the scene. A set of experiments make possible to validate the contribution of V-GPP to the SPIDERobot while operating in realistic working conditions, as well as, to evaluate the interaction between the V-GPP and the motion controlling system. The results demonstrated that the proposed robot is able to construct architectural structures and to avoid collisions with obstacles in their working environment. The V-GPP system localizes the robot with a precision of 0.006 m, detects the targets and successfully generates a path that takes into account the displacement of cables. Therefore, the results demonstrate that the SPIDERobot can be scaled up to real working conditions.
- Collaborative fault detection and diagnosis architecture for industrial cyber-physical systemsPublication . Piardi, Luis; Costa, Pedro; Oliveira, Andre Schneider; Leitão, PauloIndustrial Cyber-Physical Systems (ICPS) deploy a network of connected and heterogeneous systems, integrating computational and physical components, improving production and quality. However, a fault-free system is still utopian, but methodologies related to fault detection and diagnosis are still being treated in isolation or a centralized approach, overlooking the technological advances related to ICPS such as IoT, AI and edge computing. With this in mind, the present work proposes a collaborative architecture for fault detection and diagnosis, regarding the exchange of information for collaborative detection and diagnosis adopting disruptive technologies. Laboratory-scale ICPS experiments were carried out to compare the proposed approach with the approach where each component separately intends to identify and diagnose faults. The results present a faster response generating a system more flexible and robust.
- Collaborative fault tolerance for cyber–physical systems: The detection stagePublication . Piardi, Luís; Oliveira, André Schneider; Costa, Pedro; Leitão, PauloIn the era of Industry 4.0, fault tolerance is essential for maintaining the robustness and resilience of industrial systems facing unforeseen or undesirable disturbances. Current methodologies for fault tolerance stages namely, detection, diagnosis, and recovery, do not correspond with the accelerated technological evolution pace over the past two decades. Driven by the advent of digital technologies such as Internet of Things, cloud and edge computing, and artificial intelligence, associated with enhanced computational processing and communication capabilities, local or monolithic centralized fault tolerance methodologies are out of sync with contemporary and future systems. Consequently, these methodologies are limited in achieving the maximum benefits enabled by the integration of these technologies, such as accuracy and performance improvements. Accordingly, in this paper, a collaborative fault tolerance methodology for cyber–physical systems, named Collaborative Fault * (CF*), is proposed. The proposed methodology takes advantage of the inherent data analysis and communication capabilities of cyber–physical components. The proposed methodology is based on multi-agent system principles, where key components are self-fault tolerant, and adopts collaborative and distributed intelligence behavior when necessary to improve its fault tolerance capabilities. Experiments were conducted focusing on the fault detection stage for temperature and humidity sensors in warehouse racks. The experimental results confirmed the accuracy and performance improvements under CF* compared with the local methodology and competitiveness when compared with a centralized approach.
- Collision avoidance system with obstacles and humans to collaborative robots arms based on RGB-D dataPublication . Brito, Thadeu; Lima, José; Costa, Pedro; Matellán, Vicente; Braun, JoãoThe collaboration between humans and machines, where humans can share the same work environment without safety equipment due to the collision avoidance characteristic is one of the research topics for the Industry 4.0. This work proposes a system that acquires the space of the environment through an RGB-Depth sensor, verifies the free spaces in the created Point Cloud and executes the trajectory of the collaborative manipulator avoiding collisions. It is demonstrated a simulated environment before the system in real situations, in which the movements of pick-and-place tasks are defined, diverting from virtual obstacles with the RGB-Depth sensor. It is possible to apply this system in real situations with obstacles and humans, due to the results obtained in the simulation. The basic structure of the system is supported by the ROS software, in particular, the Movelt! and Rviz. These tools serve both for simulations and for real applications. The obtained results allow to validate the system using the algorithms PRM and RRT, chosen for being commonly used in the field of robot path planning.
- A comparison of A* and RRT* algorithms with dynamic and real time constraint scenarios for mobile robotsPublication . Braun, João; Brito, Thadeu; Lima, José; Costa, Paulo Gomes da; Costa, Pedro; Nakano, Alberto YoshiroThere is an increasing number of mobile robot applications. The demanding of the Industry 4.0 pushes the robotic areas in the direction of the decision. The autonomous robots should actually decide the path according to the dynamic environment. In some cases, time requirements must also be attended and require fast path planning methods. This paper addresses a comparison between well-known path planning methods using a realistic simulator that handles the dynamic properties of robot models including sensors. The methodology is implemented in SimTwo that allows to compare the A* and RRT* algorithms in different scenarios with dynamic and real time constraint scenarios.
- Cr(III) uptake by marine algal biomass: equilibrium and kineticsPublication . Vilar, Vítor J.P.; Freitas, Olga; Costa, Pedro; Botelho, Cidália; Martins, Ramiro; Boaventura, RuiIn this work, biosorption of trivalent chromium by the marine brown algae Sargassum muticum was 37 studied in a batch system. The effect of the solution pH on Cr(III) uptake by Sargassum was 38 investigated. Kinetics and equilibrium experiments were conducted at different pH values (3.0, 4.0 and 39 5.0). Equilibrium data are well described by the Langmuir and Langmuir-Freundlich isotherms and 40 kinetics follows the pseudo-second-order model, at different pH values. The two mass transfer models 41 give comparable results, but they did not provide a perfect representation of the sorption data. The 42 homogeneous diffusivity, Dh, was found to be around 1.6´10-8 cm2 s-1 for 100 mg l-1 Cr(III) 43 concentration. 44 Sargassum muticum was compared with the brown algae Laminaria hyperborean and the red algae 45 Gelidium sesquipedale in terms of uptake capacity. The maximum uptake capacities for Sargassum, 46 Laminaria and Gelidium were, respectively, 56 ± 3, 70 ± 4 and 18 ± 1 mg Cr(III) g-1, at pH = 5.