2001
Authors
Mendonca, H; da Silva, JM; Matos, JS;
Publication
COMPUTER STANDARDS & INTERFACES
Abstract
Analog-to-digital converter (ADC) characterization is usually performed using stationary stimuli like sine waves. However, the use of a non-stationary stimulus, besides providing testing conditions closer to those found in real applications, can lead to interesting improvements in ADC testing speed, This kind of signal needs proper processing techniques in order to extract useful information. In this paper we propose the use of joint time-frequency analysis (JTFA) for this purpose. The basic principles of the technique, and how it can be used in ADC testing are presented. in particular, a method for characterising an ADC on its entire bandwidth using a single stimulus is described.
2001
Authors
Costa, PG; Sousa, A; Marques, P; Costa, P; Gaio, S; Moreira, AP;
Publication
RoboCup 2001: Robot Soccer World Cup V
Abstract
The 5dpo team presented a solid set of innovative solutions. The overall workings of the team are presented. Mechanical and electronic solutions are explained and closed loop working is discussed. Main innovative features include I-R communications link and circular bar code for robot tracking. Low level control now presents a dynamics prediction layer for enhanced motion control. Team strategy is also new and a multi-layered high level reasoning system based on state charts allows for cooperative game play. © 2002 Springer-Verlag Berlin Heidelberg.
2001
Authors
Silva, MF; Machado, JAT; Lopes, AM;
Publication
ROMOCO'01: PROCEEDINGS OF THE SECOND INTERNATIONAL WORKSHOP ON ROBOT MOTION AND CONTROL
Abstract
This paper studies periodic gaits of multi-legged robot locomotion systems based on dynamic models, The purpose is to determine the system performance during walking and the best set of locomotion variables that minimizes the optimization indices. For that objective the prescribed motion of the robot is completely characterized in terms of several locomotion variables such as gait, duty factor, body height, step length, stroke pitch, foot clearance, link lengths, body and legs mass and cycle time. In this perspective, we formulate four performance measures of the walking robot namely, the locomobility of the foot, the mean absolute power, the mean power dispersion and the mean power lost in the joint actuators per walking distance. A set of model-based experiments reveals the influence of the locomotion variables in the proposed indices.
2001
Authors
Silva, MF; Machado, JAT; Lopes, AME;
Publication
CLIMBING AND WALKING ROBOTS
Abstract
This paper presents the energy analysis of periodic gaits for multi-legged locomotion systems. The main purpose is to determine the system performance during walking and the best set of locomotion variables that minimizes a cost function related to energy. For that objective, the prescribed motion of the robot is completely characterized in terms of several locomotion variables such as gait, duty factor, body height, step length, stroke pitch, maximum foot clearance, link lengths, body and legs mass and cycle time. In this work, we formulate three indices to quantitatively measure the performance of the walking robot namely the mean absolute power, the mean power dispersion and the mean power lost in the joint actuators. A set of experiments reveals the influence of the locomotion variables in the proposed indices.
2001
Authors
Cunha, JB; Oliveira, PBD; Cordeiro, M;
Publication
PROCEEDINGS OF THE WORLD CONGRESS OF COMPUTERS IN AGRICULTURE AND NATURAL RESOURCES
Abstract
Technologies employed in greenhouse production systems have been developed considerably during the recent decades. These improvements have taken place in many different research areas, such as the development of new covering materials and actuating equipments, modeling of the plant physiological processes and greenhouse climate, new cultural techniques, among many other topics. Although, due to economic and environmental increasing requirements there is still a need to improve the tools used for greenhouse management. At the present this work is being addressed with the emphasis on the economic optimization of the production process. This approach implies to know the influence of climate factors on production, as well the establishment of a good interface between engineers, physiologists and biologists. This paper presents the methods that are being implemented and tested with the aim of improving the climate management of a greenhouse located in the UTAD-University campus.
2001
Authors
Oliveira, PBD;
Publication
ARTIFICIAL NEURAL NETS AND GENETIC ALGORITHMS
Abstract
Genetic algorithms are proposed to design two-degrees-of-freedom non-linear PID controllers for single input-single output systems. The evolutionary scheme proposed is able to design simultaneously a feedforward compensator and a nonlinear picewise PID controller. A time-domain cost function subjected to a performance constraint is deployed in order to obtain a good compromise between the set-point tracking design and the disturbance rejection design. This evolutionary approach is illustrated by a simulation example and compared with the corresponding linear configuration.
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