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Publicações

Publicações por CRIIS

2013

A set of novel modifications to improve algorithms from the A* family applied in mobile robotics

Autores
do Nascimento, TP; Costa, P; Costa, PG; Moreira, AP; Scolari Conceição, AG;

Publicação
J. Braz. Comput. Soc.

Abstract
This paper presents a set of novel modifications that can be applied to any grid-based path planning algorithm from the A* family used in mobile robotics. Five modifications are presented regarding the way the robot sees an obstacle and its target to plan the robot's path. The modifications make it possible for the robot to get to the target faster than traditional algorithms, as well as to avoid obstacles that move as fast as (or even faster than) the robot. Some simulations were made using a crowded and highly dynamic environment with twelve randomly moving obstacles. In these first simulations, a middle sized 5DPO robot was used. Also, real experiments were made with a small-sized version of a 5DPO robot to validate the algorithm's effectiveness. In all simulations and real robot experiments the objects are considered to be moving at a constant speed. Finally, we present an overall discussion and conclusion of this paper. © 2012 The Brazilian Computer Society.

2013

Real-time tracking system for a moored oil tanker: A Kalman filter approach

Autores
Malheiros, P; Rosa Santos, P; Gonçalves, J; Costa, P; Paulo Moreira, A; Veloso Gomes, F; Taveira Pinto, F;

Publicação
Lecture Notes in Mechanical Engineering

Abstract
This paper presents a tracking system developed to study the behavior of an oil tanker moored at the Berth ‘‘A’’ of the Leixões Oil Terminal, Porto, Portugal. A brief description of the local environmental conditions and the existing operational conditions at that oil terminal are presented. Due to extreme outdoor working conditions a Kalman filter was implemented to ensure the robustness and reliability of the obtained measurements. Tests were performed in laboratory on a physical model of a moored oil tanker at a scale 1/100. The results were compared with a commercial motion capture system installed in laboratory. The presented measurement system was developed as part of the DOLPHIN project that aims to study the behavior of moored ships in harbors. © Springer International Publishing Switzerland 2013.

2013

Adaptive Image Pre-processing for Quality Control in Production Lines

Autores
Arroyo, E; Lima, J; Leitao, P;

Publicação
2013 IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY (ICIT)

Abstract
Flexible and self-adaptive behaviours in automated quality control systems are features that may significantly enhance the robustness, efficiency and flexibility of the industrial production processes. However, most current approaches on automated quality control are based on rigid inspection methods and are not capable of accommodating to disturbances affecting the image acquisition quality, fact that hast direct consequences on the system's reliability and performance. In an effort to address the problem, this paper presents the development of a self-adaptive software system designed for the pre-processing (quality enhancement) of digital images captured in industrial production lines. The approach introduces the use of scene recognition as a key-feature to allow the execution of customized image pre-processing strategies, increase the system's flexibility and enable self-adapting conducts. Real images captured in a washing machines production line are presented to test and validate the system performance. Experimental results demonstrate significant image quality enhancements and a valuable reliability improvement of the automated quality control procedures.

2013

Manipulator Path Planning for Pick-and-Place Operations with Obstacles Avoidance: An A* Algorithm Approach

Autores
Sousa e Silva, JSE; Costa, P; Lima, J;

Publicação
ROBOTICS IN SMART MANUFACTURING

Abstract
This paper presents a path planning method for pick-and-place operations with obstacles in the work environment. The method developed is designed to plan the motion of an anthropomorphic manipulator in cluttered environments. The graph search algorithm A* applied to the configuration free space is used to calculate the shortest path between two points avoiding collisions with obstacles and joint limitations. Applying this algorithm in a six dimension space presents some constraints related to memory consumption and processing time, which were tackled using configuration space partition and selecting neighbourhood cells, respectively. Using the configuration space makes it possible for the entire robot body to avoid collisions with obstacles. Moreover, the system implemented proves that applying A* in high dimension configuration spaces is possible with admissible results.

2013

Fast 3D Map Matching Localisation Algorithm

Autores
Pinto, M; Moreira, AP; Matos, A; Sobreira, H; Santos, F;

Publicação
Journal of Automation and Control Engineering - JOACE

Abstract

2013

Increasing Illumination Invariance of SURF Feature Detector through Color Constancy

Autores
Petry, MR; Moreira, AP; Reis, LP;

Publicação
PROGRESS IN ARTIFICIAL INTELLIGENCE, EPIA 2013

Abstract
Most of the original image feature detectors are not able to cope with large photometric variations, and their extensions that should improve detection eventually increase the computational cost and introduce more noise to the system. Here we extend the original SURF algorithm increasing its invariance to illumination changes. Our approach uses the local space average color descriptor as working space to detect invariant features. A theoretical analysis demonstrates the impact of distinct photometric variations on the response of blob-like features detected with the SURF algorithm. Experimental results demonstrate the effectiveness of the approach in several illumination conditions including the presence of two or more distinct light sources, variations in color, in offset and scale.

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