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Publications

Publications by João Paulo Coelho

2016

Controller System Design Using the Coefficient Diagram Method

Authors
Coelho, JP; Pinho, TM; Boaventura Cunha, J;

Publication
ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING

Abstract
Coefficient diagram method is a controller design technique for linear time-invariant systems. This design procedure occurs into two different domains: an algebraic and a graphical. The former is closely paired to a conventional pole placement method and the latter consists on a diagram whose reading from the plotted curves leads to insights regarding closed-loop control system time response, stability and robustness. The controller structure has two degrees of freedom and the design process leads to both low overshoot closed-loop time response and good robustness performance regarding mismatches between the real system and the design model. This article presents an overview on this design method. In order to make more transparent the presented theoretical concepts, examples in Matlab (R) code are provided. The included code illustrates both the algebraic and the graphical nature of the coefficient diagram design method.

2015

Extended Stability Conditions for CDM Controller Design

Authors
Coelho, JP; Boaventura Cunha, J; de Moura Oliveira, PBD;

Publication
CONTROLO'2014 - PROCEEDINGS OF THE 11TH PORTUGUESE CONFERENCE ON AUTOMATIC CONTROL

Abstract
The coefficient diagram method (CDM) is one of the easiest methods for model based control system design. Its core is based on an algebraic method but it also encompasses a graphical analysis diagram that helps the user to evaluate the three main closed-loop system requirements: dynamic behaviour, robustness and stability. This later characteristic is analysed by a set of stability conditions derived from the previous work of Lipatov and Sokolov on sufficient conditions for stability. However, in CDM, only a fraction of the total conditions are considered. This work will show that this fact increases the inconclusive area within the stability space. Moreover an extended set of CDM stability conditions, in conjunction with its graphical interpretation, will be presented.

2016

Forest-based supply chain modelling using the SimPy simulation framework

Authors
Pinho, TM; Coelho, JP; Boaventura Cunha, J;

Publication
IFAC PAPERSONLINE

Abstract
Proper management of supply chains is fundamental in the overall system performance of forest based activities. Usually, efficient, management techniques a decision support, software, which needs to be able to generate fast and effective outputs from the set of possibilities. In order to do this, it is necessary to provide accurate models representative of the dynamic interactions of systems. Due to forest-based supply chains' nature, event-based models are more suited to describe their behaviours. This work proposes the modelling and simulation of a forest based supply chain, in particular the biomass supply chain, through the SimPy framework. This Python based tool allows the modelling of discrete-event, systems using operations such as events, processes Mid resources. The developed model was used to access the impact of changes in the daily working plan in three situations. First, as a control case, the deterministic behaviour was simulated. As a second approach, a machine delay was introduced and its implications in the plan accomplishment were analysed. Finally, to better address real operating conditions, stochastic; behaviours of processing and driving times were simulated. The obtained results validate the SirriPy simulation environment as a framework for modelling supply chains in general and for the biomass problem in particular.

2015

FPGA implementation of a multi-population PBIL algorithm

Authors
Coelho, JP; Pinho, TM; Cunha, JB;

Publication
IJCCI 2015 - Proceedings of the 7th International Joint Conference on Computational Intelligence

Abstract
Evolutionary-based algorithms play an important role in finding solutions to many problems that are not solved by classical methods, and particularly so for those cases where solutions lie within extreme non-convex multidimensional spaces. The intrinsic parallel structure of evolutionary algorithms are amenable to the simultaneous testing of multiple solutions; this has proved essential to the circumvention of local optima, and such robustness comes with high computational overhead, though custom digital processor use may reduce this cost. This paper presents a new implementation of an old, and almost forgotten, evolutionary algorithm: the population-based incremental learning method. We show that the structure of this algorithm is well suited to implementation within programmable logic, as compared with contemporary genetic algorithms. Further, the inherent concurrency of our FPGA implementation facilitates the integration and testing of micro-populations. Copyright

2016

Modelling a biomass supply chain through discrete-event simulation

Authors
Pinho, TM; Coelho, JP; Paulo Moreira, AP; Boaventura Cunha, J;

Publication
IFAC PAPERSONLINE

Abstract
The organizational struck of the companies in the biomass energy sector, regarding the supply chain management, services, can be greatly improved through the use of software decision support. tools. These tools should be able to provide real-time alternative scenarios when deviations from the initial production plans are observed. To make this possible it is necessary to have representative production chain process models where several scenarios and solutions can be evaluated accurately. Due to its nature, this type of process is more adequately represented by means of event-based models. to particular, this work presents the modelling a typical biomass production chain using the computing platform SIMEVENTS. Throughout the article details about the conceptual model, as well as simulation results, are provided.

2017

Brain emotional learning based control of a SDOF structural system with a MR damper

Authors
César, MB; Gonçalves, J; Coelho, J; De Barros, RC;

Publication
Lecture Notes in Electrical Engineering

Abstract
This paper describes the application of a Brain Emotional Learning (BEL) controller to improve the response of a SDOF structural system under an earthquake excitation using a magnetorheological (MR) damper. The main goal is to study the performance of a BEL based semi-active control system to generate the control signal for a MR damper. The proposed approach consists of a two controllers: a primary controller based on a BEL algorithm that determines the desired damping force from the system response and a secondary controller that modifies the input current to the MR damper to generate a reference damping force. A parametric model of the damper is used to predict the damping force based on the piston motion and also the current input. A Simulink model of the structural system is developed to analyze the effectiveness of the semi-active controller. Finally, the numerical results are presented and discussed. © Springer International Publishing Switzerland 2017.

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