2009
Autores
Marcal, ARS; Rodrigues, A; Cunha, M;
Publicação
2009 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM, VOLS 1-5
Abstract
The segmentation stage is a key aspect of an object-based image analysis system. However, the segmentation quality is usually difficult to evaluate for satellite images The Synthetic Image TEsting Framework (SITEF) is a tool to evaluate and compare image segmentation results. This paper presents the SITEF with an extension to model adjacency effects between neighboring parcels, using the sensor's point spread function and a grid offset A practical application of SITEF is presented using a SPOT HRG satellite image, with 6 vegetation land cover classes identified on a mountainous area The segmentation results were evaluated under various perspectives, including the parcel size and shape, the land cover types, the sensor grid offset and one parameter used in the segmentation algorithm.
2008
Autores
Mendonca, HS; da Silva, JM; Matos, JS;
Publicação
IET SCIENCE MEASUREMENT & TECHNOLOGY
Abstract
A procedure is proposed to estimate an analogue-to-digital converter's signal-to-noise plus distortion ratio using the histogram method. The procedure provides results that are in close agreement with the ones obtained with the spectral analysis and sinewave fitting methods. It is shown that the errors obtained by using former implementations of the histogram method are due to not considering the input stimulus probability density function, and it is shown how these errors can be rectified.
2008
Autores
Oliveira, HP; Sousa, AJ; Moreira, AP; Costa, PJ;
Publicação
ICINCO 2008: PROCEEDINGS OF THE FIFTH INTERNATIONAL CONFERENCE ON INFORMATICS IN CONTROL, AUTOMATION AND ROBOTICS, VOL RA-1: ROBOTICS AND AUTOMATION, VOL 1
Abstract
Omni-directional robots are becoming more and more common in recent robotic applications. They offer improved ease of maneuverability and effectiveness at the expense of increased complexity. Frequent applications include but are not limited to robotic competitions and service robotics. The goal of this work is to find a precise dynamical model in order to predict the robot behavior. Models were found for two real world omni-directional robot configurations and their parameters estimated using a prototype that can have 3 or 4 wheels. Simulations and experimental runs are presented in order to validate the presented work.
2008
Autores
Lima, JL; Goncalves, JC; Costa, PG; Moreira, AP;
Publicação
2008 IEEE INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, PROCEEDINGS
Abstract
This paper describes a joint trajectory optimized controller for a humanoid robot simulator following the real robot characteristics. As simulation is a powerful tool for speeding up the control software development, the proposed accurate simulator allows to fulfill this goal. The simulator, based on the Open Dynamics Engine and GLScene graphics library, provides instant visual feedback. The proposed simulator, with realistic dynamics, allows to design and test behaviours and control strategies without access to the real hardware in order to carry out research on robot control without damaging the real robot in the early stages of the development. The joints controller techniques, such as acceleration, speed and energy consumption minimization are discussed and experimental results are presented in order to validate the proposed simulator.
2008
Autores
Goncalves, J; Lima, J; Costa, P;
Publicação
2008 IEEE INTERNATIONAL SYMPOSIUM ON INDUSTRIAL ELECTRONICS, VOLS 1-5
Abstract
This paper describes a robust localization system, similar to the used by the teams participating in the Robocup Small size league (SLL). The system, developed in Object Pascal, allows real-time localization and control of an autonomous onmidirectional mobile robot. The localization algorithm is done resorting to odometry and global vision data fusion, applying an extended Kalman filter.
2008
Autores
Conceicao, AS; Moreira, AP; Costa, PJ;
Publicação
OPTIMAL CONTROL APPLICATIONS & METHODS
Abstract
This paper presents a nonlinear model-based predictive controller (NMPC) for trajectory tracking of a four-wheeled omnidirectional mobile robot. Methods of numerical optimization to perform real-time nonlinear minimization of the cost function are used. The cost function penalizes the robot's position error, the robot's orientation angle error, and the control effort. Experimental results of the trajectories following and the performances of the methods of optimization are presented. Copyright (C) 2007 John Wiley & Sons, Ltd.
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