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Publications

Publications by CPES

2016

Indoor localization using barely perceptible audio signals

Authors
Moutinho, J; Freitas, D; Araújo, RE;

Publication
U.Porto Journal of Engineering

Abstract
This paper presents a new approach to an audio-based indoor localization system. By using audio signals emitted by a public address sound system, mobile devices may globally localize themselves in an indoor environment where global navigation satellite systems are not viable or reliable. The use of data hiding techniques such as spread spectrum coding or echo hiding has allowed to convey information to a receiver avoiding people’s perception of the added audio content. Results demonstrate a relatively quite good localization with centimetre accuracy and precision and successful data transmission using barely perceptible audio signals.

2016

Model-based predictive control implementation for cooperative adaptive cruise control

Authors
Lopes, A; Araújo, RE;

Publication
U.Porto Journal of Engineering

Abstract
The automation of road vehicles has become a necessity to improve the efficiency and safety of this system. In a vehicle formation it is important to maintain a safety distance between the vehicles. The control of a vehicle spacing distance and longitudinal velocity can be achieved through the implementation of a model-based predictive controller. This implementation of a cooperative adaptive cruise control allows the access of another vehicle state information through vehicular communication technology and promote state prediction and ultimately system stability. The optimization algorithm performs the computation of the control input in a control horizon window and ensures that the spacing error takes only positive values. The results of the proposed controller are evaluated through the computational tool Simulink in the two-vehicle platoon. The controller is implemented in the precedent vehicle. To assess the performance of the proposed controller different control parameters and constraints were used.

2016

Assessment of Robotic Picking Operations Using a 6 Axis Force/Torque Sensor

Authors
Moreira, E; Rocha, LF; Pinto, AM; Moreira, AP; Veiga, G;

Publication
IEEE ROBOTICS AND AUTOMATION LETTERS

Abstract
This letter presents a novel architecture for evaluating the success of picking operations that are executed by industrial robots. It is formed by a cascade of machine learning algorithms (kNN and SVM) and uses information obtained by a 6 axis force/torque sensor and, if available, information from the built-in sensors of the robotic gripper. Beyond measuring the success or failure of the entire operation, this architecture makes it possible to detect in real-time when an object is slipping during the picking. Therefore, force and torque signatures are collected during the picking movement of the robot, which is decomposed into five different stages that allows to characterize distinct levels of success over time. Several trials were performed using an industrial robot with two different grippers for picking a long and flexible object. The experiments demonstrate the reliability of the proposed approach under different picking scenarios since, it obtained a testing performance (in terms of accuracy) up to 99.5% of successful identification of the result of the picking operations, considering an universe of 400 attempts.

2016

An Optimization Approach for the Inverse Kinematics of a Highly Redundant Robot

Authors
Costa, P; Lima, J; Pereira, AI; Costa, P; Pinto, A;

Publication
PROCEEDINGS OF THE SECOND INTERNATIONAL AFRO-EUROPEAN CONFERENCE FOR INDUSTRIAL ADVANCEMENT (AECIA 2015)

Abstract
This 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.

2016

The SPIDERobot: A Cable-Robot System for On-site Construction in Architecture

Authors
Sousa, JP; Palop, CG; Moreira, E; Pinto, AM; Lima, J; Costa, P; Costa, P; Veiga, G; Paulo Moreira, A;

Publication
Robotic Fabrication in Architecture, Art and Design 2016

Abstract
The use of robots in architectural construction has been a research field since the 1980s. Driven by both productive and creative concerns, different systems have been devised based on large-scale robotic structures, mobile robotic units or flying robotic vehicles. By analyzing these approaches and discussing their advantages and limitations, this paper presents an alternative strategy to automate the building construction processes in on-site scenarios. The SPIDERobot is a cable-robot system developed to perform assembly operations, which is driven by a specific Feedback Dynamic Control System (FDCS) based on a vision system. By describing and illustrating this research work, the authors argue about the advantages of this cable robot system to deal with the complexity and the scale of building construction in architecture. © Springer International Publishing Switzerland 2016.

2016

The Impact of Convergence Cameras in a Stereoscopic System for AUVs

Authors
Aguiar, J; Pinto, AM; Cruz, NA; Matos, AC;

Publication
IMAGE ANALYSIS AND RECOGNITION (ICIAR 2016)

Abstract
Underwater imaging is being increasingly helpful for the autonomous robots to reconstruct and map the marine environments which is fundamental for searching for pipelines or wreckages in depth waters. In this context, the accuracy of the information obtained from the environment is of extremely importance. This work presents a study about the accuracy of a reconfigurable stereo vision system while determining a dense disparity estimation for underwater imaging. The idea is to explore the advantage of this kind of system for underwater autonomous vehicles (AUV) since varying parameters like the baseline and the pose of the cameras make possible to extract accurate 3D information at different distances between the AUV and the scene. Therefore, the impact of these parameters is analyzed using a metric error of the point cloud acquired by a stereoscopic system. Furthermore, results obtained directly from an underwater environment proved that a reconfigurable stereo system can have some advantages for autonomous vehicles since, in some trials, the error was reduced by 0.05m for distances between 1.125 and 2.675 m.

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