Jesus Gonzalez

On robust chaos suppression in a class of nondriven oscillators: application to the Chua's circuit

This paper deals with a feedback control strategy for chaos suppression. The proposed strategy is an input-output control scheme which comprises an uncertainty estimator and an asymptotic linearizing feedback. The developed control scheme allows chaos suppression in spite of modeling errors and parametric variations.

A time delay coordinates strategy to control a class of chaotic oscillators

Abstract A time delay coordinates (TDC) strategy to control a class of chaotic oscillators is studied. The class of chaotic systems includes both externally and parametrically excited systems, such as the Duffing and the Coulombic oscillators. By assuming that the exact model of the system is not known and that position is the only state available for measurements, the controller comprises a linearizing-like feedback and an uncertainty estimator. Simulations are provided to illustrate the performance of the controller.

A discrete approach to the control and synchronization of a class of chaotic oscillators

This work deals with the control and synchronization of chaotic systems. In the first part of the work, a general discrete-time strategy is developed to control a class of second-order uncertain nonlinear systems. The proposed strategy is based on an iterative procedure, borrowed from contraction map methodologies, and provides estimates of unmeasured states and modeling errors. Nonidentical chaotic systems can be synchronized by means of the proposed strategy. By assuming that the exact model of the oscillators is not known and that position is the only state available for measurements, the robust synchronization scheme comprises a recursive feedback-control law. Computer simulations are provided to illustrate the operation of the designed synchronization scheme.

Linearizing control of a binary distillation column based on a neuro-estimator

Abstract In this work, the LV-control problem in binary distillation columns is addressed. With least prior knowledge, a linear reference model with unknown terms is obtained. The time variations of the unknown terms are estimated using two on-line trained perceptrons. These estimates are subsequently used to design a feedback linearizing-like controller. The closed-loop behavior is analyzed through numerical examples. The resulting controller shows robustness against external disturbances and set-point changes.

Control of a fluid catalytic cracking unit based on proportional-integral reduced order observers

Abstract The fluid catalytic cracking (FCC) unit is one of the most complex interactive processes in the refining industry, and is difficult to operate and control. This work deals with the regulative control law design for stabilization of the reactor and regenerator temperatures, considering that the kinetics terms are poorly known. The proposed control law makes use of on-line estimates of the input/output modeling errors, obtained from a proportional-integral reduced order observer. The structure of the proposed controller is similar to a proportional-double integral compensator (PI 2 ) such that a new parameterization of the controllers gains is given in terms of the closed-loop and estimation time constants. The performance of the control scheme proposed here is analyzed via numerical simulations.

CFD Simulation Gas-Liquid Flow in a Copper Converter with Bottom Air Injection

Peirce-Smith converters (PSC) are chemical reactors where copper matte reacts with air. A conventional PSC is a long horizontal cylinder where air is injected laterally into the cooper bath through submerged tuyeres. In these PSC, air is injected at high velocities to obtain an adequate mixing of the copper bath and to avoid tuyere blockage. An alternative PSC configuration uses top blowing of air accompanied by gentle nitrogen bottom stirring. In this work, the direct bottom injection of air at low inlet velocity was studied by means of transient multiphase 3D CFD numerical simulations considering three blowing conditions. The ?-? turbulence model and the volume of fluid model (VOF) were used in order to model the turbulent nature of the flow and to deal with the multiphase flow. Special attention was paid to the air bubbles formation and its effect on the copper bath mixing. The dynamic behavior of turbulent kinetic energy and the average velocity of the copper matte were analyzed. The numerical simulations suggest that the relationship between air inlet velocity and bath mixing is non linear. However, using the air bottom injection at low velocities, the obtained copper bath nominal velocity is similar to that reported in a conventional PSC.

Carbon estimation of steel in a BOF with noise attenuation

Abstract The estimation problem of carbon content of molten steel in a Basic Oxygen Furnace is addressed in this work. It is assumed that only measurements of carbon monoxide content of off-gas are available. Given that such measurements are corrupted with noise, determining the carbon from the thermodynamic equilibrium relationship yields poor results. Due to this, an integral estimator with noise attenuation is proposed. Results of numerical simulations show a good agreement between the actual carbon content and the estimated value.

Nonlinear recursive feedback control for the regulation of substrate concentration in a fixed bed bioreactor

In this work, a recursive nonlinear feedback control law for the regulation of the outlet substrate concentration for a fixed bed bioreactor with immobilized biomass is designed. The control algorithm is based on a reduced order model related with ordinary differential equations and only made use of a discrete substrate outlet concentration for its implementation. It is shown that the proposed control algorithm is robust against disturbances in the input substrate concentration. The performance of the proposed regulation scheme is illustrated by means of numerical simulations.

CFD Analysis of Multiphase Flow in a Slab Continuous Caster Mold

In order to analyze the influence of a third phase in the behaviour of the free surface profile in the mould of a slab steel continuous caster, multiphase flow in a mould water model is physically and numerically investigated. A one third scale mould water model was constructed in accordance with the Froude similarity criterion. The free surface profile in the experimental air-water system was tracked using ultrasonic level sensors which were located at six different positions along a line between the submerged entry nozzle and the mould narrow wall. Volumetric flow rates of water from 3.5×10-4 to 5.83×10-4 m3 /s were employed in the physical experiments. Three submergence depths of the nozzle, namely 0.05, 0.07 and 0.09 m, were considered. On the other hand, two and three phase transient and steady state numerical simulations were carried out by means of computational fluid dynamics software. Oil engine was employed as the third phase in the numerical simulations. A comparison between the experimental results and the numerical ones with three phases suggests significant changes in the steel-slag interface due to the presence of the third phase, particularly in the neighbourhood of the discharge of the submerged entry nozzle.Copyright

Optimization of the level sensor position for a continuous slab caster

The optimal position of the mold liquid level sensor for a continuous slab caster is experimentally studied in this work. To establish the optimal position, a 1:1/3 physical cold water model was employed. The water model was constructed in accordance with the Froude similarity criterion. The meniscus profile dispersion was evaluated at several volumetric flow rates and submerged entry nozzle (SEN) submergence depths. The liquid level measurements were taken with an ultrasonic distance sensor and recorded in a computer. The experimental results show a strong nonlinear correlation between the process parameters and meniscus fluctuations intensity.