Cookies Policy
The website need some cookies and similar means to function. If you permit us, we will use those means to collect data on your visits for aggregated statistics to improve our service. Find out More
Accept Reject
  • Menu
Publications

Publications by CRIIS

2010

Multi-criteria Manipulator Trajectory Optimization Based on Evolutionary Algorithms

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

Publication
SOFT COMPUTING MODELS IN INDUSTRIAL AND ENVIRONMENTAL APPLICATIONS

Abstract
This paper proposes a method, based on a genetic algorithm, to generate smoth manipulator trajectories in a multi-objective perspective. The method uses terms proportional to the integral of the squared displacements in order to eliminate the jerk movement. In this work, the algorithm, based on NSGA-II and maximin sorting schemes, considers manipulators of two, three and four rotational axis (2R, 3R, 4R). The efficiency of the algorithm is evaluated, namely the extension of the front and the dispersion along the front. The effectiveness and capacity of the proposed approach are shown through simulations tests.

2010

Greenhouse Heat Load Prediction Using a Support Vector Regression Model

Authors
Coelho, JP; Cunha, JB; Oliveira, PD; Pires, ES;

Publication
SOFT COMPUTING MODELS IN INDUSTRIAL AND ENVIRONMENTAL APPLICATIONS

Abstract
Modern greenhouse climate controllers are based on models in order to simulate and predict the greenhouse environment behaviour. These models must be able to describe indoor climate process dynamics, which are a function of both the control actions taken and the outside climate. Moreover, if predictive or feedforward control techniques are to be applied, it is necessary to employ models to describe and predict the weather. From all the climate variables, solar radiation is the one with greater impact in the greenhouse heat load. Hence, making good predictions of this physical quantity is of extreme importance. In this paper, the solar radiation is represented as a time-series and a support vector regression model is used to make long term predictions. Results are compared with the ones achieved by using other type of models, both linear and non-linear.

2010

Maximin Spreading Algorithm

Authors
Solteiro Pires, EJS; Mendes, L; Lopes, AM; de Moura Oliveira, PBD; Tenreiro Machado, JAT; Vaz, J; Rosario, MJ;

Publication
2010 IEEE CONGRESS ON EVOLUTIONARY COMPUTATION (CEC)

Abstract
This paper presents a genetic algorithm to optimize uni-objective problems with an infinite number of optimal solutions. The algorithm uses the maximin concept and epsilon-dominance to promote diversity over the admissible space. The proposed algorithm is tested with two well-known functions. The practical results of the algorithm are in good agreement with the optimal solutions of these functions. Moreover, the proposed optimization method is also applied in two practical real-world engineering optimization problems, namely, in radio frequency circuit design and in kinematic optimization of a parallel robot. In all the cases, the algorithm draws a set of optimal solutions. This means that each problem can be solved in several different ways, all with the same maximum performance.

2010

Improving disturbance rejection of PID controllers by means of the magnitude optimum method

Authors
Vrancic, D; Strmcnik, S; Kocijan, J; de Moura Oliveira, PBD;

Publication
ISA TRANSACTIONS

Abstract
The magnitude optimum (MO) method provides a relatively fast and non-oscillatory closed-loop tracking response for a large class of process models frequently encountered in the process and chemical industries. However, the deficiency of the method is poor disturbance rejection performance of some processes. in this paper, disturbance rejection performance of the PID controller is improved by applying the "disturbance rejection magnitude optimum" (DRMO) optimisation method, while the tracking performance has been improved by a set-point weighting and set-point filtering PID controller structure. The DRMO tuning method requires numerical optimisation for the calculation of PID controller parameters. The method was applied to two different 2-degrees-of-freedom PID controllers and has been tested on several different representatives of process models and one laboratory set-up. A comparison with some other tuning methods has shown that the proposed tuning method, with a set-point filtering PID controller, is quite efficient in improving disturbance rejection performance, while retaining tracking performance comparable with the original MO method.

2010

Particle swarm optimization with fractional-order velocity

Authors
Pires, EJS; Machado, JAT; Oliveira, PBD; Cunha, JB; Mendes, L;

Publication
NONLINEAR DYNAMICS

Abstract
This paper proposes a novel method for controlling the convergence rate of a particle swarm optimization algorithm using fractional calculus (FC) concepts. The optimization is tested for several well-known functions and the relationship between the fractional order velocity and the convergence of the algorithm is observed. The FC demonstrates a potential for interpreting evolution of the algorithm and to control its convergence.

2010

AUTOMATED DESIGN OF MICROWAVE DISCRETE TUNING DIFFERENTIAL CAPACITANCE CIRCUITS IN Si-INTEGRATED TECHNOLOGIES

Authors
Mendes, L; Solteiro Pires, EJS; Vaz, JC; Rosario, MJ; de Moura Oliveira, PBDM; Tenreiro Machado, JAT;

Publication
MICROWAVE AND OPTICAL TECHNOLOGY LETTERS

Abstract
A genetic algorithm used to design radio-frequency binary-weighted differential switched capacitor arrays (RFDSCAs) is presented in this article. The algorithm provides a set of circuits all having the same maximum performance. Thus article also describes the design. implementation. and measurements results of a 0 25 mu m BiCMOS 3-bit RFDSCA. The experimented results show that the circuit presents the expected performance up to 40 GHz. The similarity between the evolutionary solutions, circuit simulations, and measured results indicates that the genetic synthesis method is a very useful tool for designing opitmum performance RFDSCAs (C) 2010 Wiley Periodicals, Inc Microwave Opt Technol Lett 52, 629-634, 2010. Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.25009

  • 279
  • 331