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Publicações

Publicações por CRIIS

2003

Cascade control of a hexapod robot

Autores
Silva, MF; Machado, JAT; Lopes, AM;

Publicação
CLIMBING AND WALKING ROBOTS: AND THEIR SUPPORTING TECHNOLOGIES

Abstract
This paper analyzes the performance of a hexapod robot under the action of a cascade controller involving position and force feedback loops. In order to evaluate the system properties we formulate several measures of the walking system based on the system dynamics and the trajectory errors. Simulation experiments reveal the influence of the different control algorithms upon the proposed indices.

2003

Fractional order dynamics in a GA planner

Autores
Pires, EJS; Machado, JAT; Oliviera, PBD;

Publicação
SIGNAL PROCESSING

Abstract
This work addresses the signal propagation and the fractional-order dynamics during, the evolution of a genetic algorithm (GA), for generating a robot manipulator trajectory. The GA objective is to minimize the trajectory space/time ripple without exceeding the torque requirements. In order to investigate the phenomena involved in the GA population evolution, the mutation is exposed to excitation perturbations and the corresponding fitness variations are evaluated. The chaos-like noise and the input/output signals are studied revealing a fractional-order dynamics, characteristic of a long-term system memory.

2003

Fractional order dynamics in a genetic algorithm

Autores
Pires, EJS; Machado, JAT; Oliveira, PBD;

Publicação
PROCEEDINGS OF THE 11TH INTERNATIONAL CONFERENCE ON ADVANCED ROBOTICS 2003, VOL 1-3

Abstract
This work addresses the fractional-order dynamics during the evolution of a Genetic Algorithm population (GA) for generating a robot manipulator trajectory. The GA objective is to minimize the trajectory space/time ripple without exceeding the torque requirements. In order to investigate the phenomena involved in the GA population evolution, the mutation is exposed to excitation perturbations and the corresponding fitness variations are evaluated. The input/output signals are studied revealing a fractional-order dynamic evolution, characteristic of a long-term system memory.

2003

Continuous function optimisation using a hybrid split particle swarm algorithm

Autores
Oliveira, PBD;

Publicação
INTELLIGENT CONTROL SYSTEMS AND SIGNAL PROCESSING 2003

Abstract
A new optimisation algorithm is proposed that results from merging a split adaptive particle swarm optimisation algorithm with the differential evolution algorithm. The proposed technique adopts the crossover type of operator used within the differential evolution algorithm to update the swarm particle velocity vectors. The hybrid algorithm is tested in a well known benchmark continuous function and its performance compared with the particle swarm optimisation and differential evolution algorithms. Copyright (C) 2003 IFAC.

2003

Fractional order dynamical phenomena in a GA

Autores
Pires, EJS; Machado, JAT; Oliveira, PBD;

Publicação
GENETIC AND EVOLUTIONARY COMPUTATION - GECCO 2003, PT I, PROCEEDINGS

Abstract
This work addresses the fractional-order dynamics during the evolution of a GA, which generates a robot manipulator trajectory. In order to investigate the phenomena involved in the GA population evolution, the crossover is exposed to excitation perturbations and the corresponding fitness variations are evaluated. The input/output signals are studied revealing a fractional-order dynamic evolution, characteristic of a long-term system memory.

2003

A CMOS mixed-signal interface with a RF transmitter for a micromachined soil moisture sensor

Autores
Morais, R; Valente, A; Correia, JH; Couto, C;

Publicação
2003 IEEE INTERNATIONAL SYMPOSIUM ON INDUSTRIAL ELECTRONICS, VOLS 1 AND 2

Abstract
This paper describes a CMOS mixed-signal interface with a RF transmitter. This die is assembled in a Multi-Chip-Module (MCM) micro-system together with the micromachined soil moisture sensor to achieve a cost-effective solution with accurate and reliable measurements for soil moisture in agriculture. The soil moisture probe, based on Dual-Probe Heat-Pulse (DPHP) method, is fabricated in bulk-micromachining technology. The DPHP method is based on the measurement of the maximum temperature rise at some distance from the heater, after applying a heat-pulse. The measurement of the temperature rise is obtained by subtracting soil temperature from the probe temperature. The mixed-signal interface is based on a pre-amplification stage and first-order sigma-delta modulator. The bit-stream output of the modulator is then applied to a counter as a first order decimation filter thus providing a 12-bit readout sample. Prior to transmission, data is encoded as a pulse width modulated (PWM) signal and then transmitted by means of an amplitude shift-keying (ASK) modulation. ne transmitter features a VCO phase locked to the quartz crystal reference of 13.56 MHz to achieve a carrier frequency of 433.92 MHz. A RF power amplifier based on class E topology was chosen. The CMOS mixed-signal interface with a RF transmitter has been implemented in a single-chip using a standard CMOS process (AMI 0.7 mum, n-well, 2 metals and I Poly).

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