Scielo RSS <![CDATA[Latin American applied research]]> http://www.scielo.org.ar/rss.php?pid=0327-079320060002&lang=es vol. 36 num. 2 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.ar/img/en/fbpelogp.gif http://www.scielo.org.ar <![CDATA[An extended MPC convergence condition]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200001&lng=es&nrm=iso&tlng=es Nominal convergence of Constrained Model Predictive Control has been extensively analyzed in the last fifteen years. The inclusion of a terminal constraint into the optimization problem and the expansion of the prediction horizon up to infinity are the main strategies already proposed in order to achieve the desired stability. However, when a model is used in which the inputs are in the incremental form, these strategies tend to be infeasible. This paper extends the contracting constraint idea by including a simple-to-apply and less restrictive new set of constraints into the optimization problem, to allow nominal convergence. <![CDATA[Centralized formation control of non-holonomic mobile robots]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200002&lng=es&nrm=iso&tlng=es This work presents a control algorithm for a group of non-holonomic mobile robots that must attain coordinately a specific formation, which can be fixed or moving in the work space. The control error is defined in terms of location, size and shape of the constellation of points placed by the robots and the constellation of objective points. The stability analysis of the proposed control system is included along with the results from simulation and laboratory experiencies which validate the good performance of this robot formation control system. <![CDATA[Stable AGV corridor navigation based on data and control signal fusion]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200003&lng=es&nrm=iso&tlng=es This work presents a control strategy for mobile robots navigating in corridors, using the fusion of the control signals from two redundant or homogeneous controllers: one based on optical flow calculation and the other based on the estimates of position of the robot with respect to the centerline of the corridor, which is estimated using data from ultrasonic and vision sensors. Both controllers generate angular velocity commands to keep the robot navigating along the corridor, compensating for the dynamics of the robot. The fusion of both control signals is done through a Decentralized Information Filter. The stability of the resulting control system is analyzed. Experiments on a laboratory robot are presented to show the feasibility and performance of the proposed control system. <![CDATA[Teleoperation of mobile robots]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200004&lng=es&nrm=iso&tlng=es This paper proposes a stable control structure for bilateral teleoperation of mobile robots. The proposed control structure includes a time-delay compensation placed on both the local and remote sites of the teleoperation system. Teleoperation experiments through a simulated and real (using Internet) communication channel are presented to illustrate the performance and stability of the proposed control structure. <![CDATA[The EEG forward problem: theoretical and numerical aspects]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200005&lng=es&nrm=iso&tlng=es We focus on the Forward Problem of electroencephalography, discuss a mathematical model and state properties of its weak solutions. A static and a time-dependent model for the source are considered. Numerical solutions, obtained by a Boundary Element Method technique, are compared with the analytical ones and with EEG recordings. <![CDATA[Supervisory control of an HEV using an inventory control approach]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200006&lng=es&nrm=iso&tlng=es Hybrid electric vehicles (HEV) are those equipped with two or more energy sources, usually, a fuel tank with its associated internal combustion engine (ICE) and an electrical storage system (ESS), typically a bank of batteries. In order to efficiently operate the system it is necessary to determine the instantaneous power split between the two sources when the vehicle performs a predetermined duty cycle. In this work, this problem is posed as an optimal control problem with constraints, specifically, as an inventory control problem and solved using dynamic programming (DP). Results obtained for the HEV being developed in the Applied Electronics Group, School of Engineering, National University of Río Cuarto are shown. <![CDATA[A third order discrete event method for continuous system simulation]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200007&lng=es&nrm=iso&tlng=es This paper introduces a new numerical method for integration of ordinary differential equations. Following the idea of quantization based integration, i.e., replacing the time discretization by state quantization, this new method performs a third order approximation allowing to achieve better accuracy than their first and second order predecessors. It is shown that the new algorithm satisfies the same theoretical properties of the previous methods and also shares their main advantages in the integration of discontinuous systems. <![CDATA[An observer for controlled Lipschitz continuous systems]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200008&lng=es&nrm=iso&tlng=es In this paper we present an observer for controlled nonlinear systems that are locally Lipschitz continuous in both the state and control variables. This observer is based on a recently introduced model of observer for autonomous Lypschitz continuous systems, and can be designed to realize an arbitrary, finite accuracy when both the state space and control variables evolve in bounded regions. <![CDATA[On the use of Lee's protocol for speckle-reduncing techniques]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200009&lng=es&nrm=iso&tlng=es This paper presents two new MAP (Maximum a Posteriori) filters for speckle noise reduction and a Monte Carlo procedure for the assessment of their performance. In order to quantitatively evaluate the results obtained using these new filters, with respect to classical ones, a Monte Carlo extension of Lee's protocol is proposed. This extension of the protocol shows that its original version leads to inconsistencies that hamper its use as a general procedure for filter assessment. Some solutions for these inconsistencies are proposed, and a consistent comparison of speckle-reducing filters is provided. <![CDATA[Adaptive filtering using projection onto convex sets]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200010&lng=es&nrm=iso&tlng=es In this paper we propose a novel adaptive filtering algorithm. The algorithm exploits the information given by the power spectral density of the noise extracted from the pe-riodogram of filtering error. The goal is try to match the spectral properties of the error filtering with the spectral properties of the measurement noise. With this in mind appropriate convex and closed sets are built and projections onto them are computed. The simulation results show that the algorithm has excellent convergence properties with a reduced number of updates. This could be exploited to obtain a lower computational load. <![CDATA[On-line costate integration for nonlinear control]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0327-07932006000200011&lng=es&nrm=iso&tlng=es The optimal feedback control of nonlinear chemical processes, specially for regulation and set-point changing, is attacked in this paper. A novel procedure based on the Hamiltonian equations associated to a bilinear approximation of the dynamics and a quadratic cost is presented. The usual boundary-value situation for the coupled state-costate system is transformed into an initial-value problem through the solution of a generalized algebraic Riccati equation. This allows to integrate the Hamiltonian equations on-line, and to construct the feedback law by using the costate solution trajectory. Results are shown applied to a classical nonlinear chemical reactor model, and compared against standard MPC and previous versions of bilinear-quadratic strategies based on power series expansions.