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Publications

Publications by CRAS

2016

Towards a Reliable Robot for Steep Slope Vineyards Monitoring

Authors
dos Santos, FN; Sobreira, H; Campos, D; Morais, R; Moreira, AP; Contente, O;

Publication
JOURNAL OF INTELLIGENT & ROBOTIC SYSTEMS

Abstract
Develop ground robots for crop monitoring and harvesting in steep slope vineyards is a complex challenge. Because of two main reasons: harsh condition of the terrain and unstable localization accuracy got from Global Positioning Systems (GPS). This paper presents a hybrid SLAM (VineSLAM) considering low cost landmarks to increase the robot localization accuracy, robustness and redundancy on these steep slope vineyards. Also, we present a cost-effective robot to carry-out crop monitoring tasks in steep slope vineyard environment. Test results got in a simulated and in a real test case supports the proposed approach and robot.

2016

Reduction of Drying Process Time of Natural Cork Stoppers Process in Lean Improvement Efforts

Authors
Pinho, TM; Campos, D; Boaventura-Cunha, J; Azevedo, A; Paulo Moreira, A;

Publication
Lecture Notes in Management and Industrial Engineering - Engineering Systems and Networks

Abstract

2016

Quadripole models for simulation and leak detection on gas pipelines

Authors
Baltazar, S; Azevedo Perdicoúlis, TP; Lopes dos Santos, P;

Publication
PSIG Annual Meeting 2016

Abstract
This work focus on the simulation of gas pipeline dynamic models in view to develop a leakage detection tool. The gas dynamics in the pipes is represented by a system of nonlinear partial differential equations. The linear partial differential equations is reduced to a transfer function model. Taking advantage of an electrical analogy, a pipeline can be represented by a two port network where gas mass flows behave like electrical currents and pressures like voltages. Thence, four transfer functions quadripole models are found to describe the gas pipeline dynamics, depending on the variable of interest at the boundaries. These models are simple enough to be used in the control and management of the network. These models have been validated using operational data and used to simulate a leakage. © Copyright 2016, PSIG, Inc.

2016

Subspace Algorithm for Identifying Bilinear Repetitive Processes with Deterministic Inputs

Authors
Ramos, JA; Rogers, E; dos Santos, PL; Perdicoulis, T;

Publication
2016 EUROPEAN CONTROL CONFERENCE (ECC)

Abstract
In this paper we introduce a bilinear repetitive process and present an iterative subspace algorithm for its identification. The advantage of the proposed approach is that it overcomes the "curse of dimensionality", a hurdle commonly encountered with classical bilinear subspace identification algorithms. Simulation results show that the algorithm converges quickly and provides new alternatives for modeling/identifying nonlinear repetitive processes.

2016

State Space LPV Model Identification Using LS-SVM: A Case-Study with Dynamic Dependence

Authors
Romano, RA; dos Santos, PL; Pait, F; Perdicoulis, TP;

Publication
2016 IEEE CONFERENCE ON CONTROL APPLICATIONS (CCA)

Abstract
In this paper the nonparametric identification of state-space linear parameter-varying models with dynamic mapping between the scheduling signal and the model matrices is considered. Indeed, we are particularly interested on the problem of estimating a model using data generated from an LPV system with static dependence, which is however represented on a different state-basis from the one considered by the estimator.

2016

Machine Learning Barycenter Approach to Identifying LPV State-Space Models

Authors
Romano, RA; dos Santos, PL; Pait, F; Perdicoulis, TP; Ramos, JA;

Publication
2016 AMERICAN CONTROL CONFERENCE (ACC)

Abstract
In this paper an identification method for statespace LPV models is presented. The method is based on a particular parameterization that can be written in linear regression form and enables model estimation to be handled using Least-Squares Support Vector Machine (LS-SVM). The regression form has a set of design variables that act as filter poles to the underlying basis functions. In order to preserve the meaning of the Kernel functions (crucial in the LS-SVM context), these are filtered by a 2D-system with the predictor dynamics. A data-driven, direct optimization based approach for tuning this filter is proposed. The method is assessed using a simulated example and the results obtained are twofold. First, in spite of the difficult nonlinearities involved, the nonparametric algorithm was able to learn the underlying dependencies on the scheduling signal. Second, a significant improvement in the performance of the proposed method is registered, if compared with the one achieved by placing the predictor poles at the origin of the complex plane, which is equivalent to considering an estimator based on an LPV auto-regressive structure.

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