Nonlinear and robust control strategy based on chemotherapy to minimize the HIV concentration in blood plasma

"A nonlinear PI-type control strategy is designed in order to minimize the HIV concentration in blood plasma, via medical drug injection, under the framework of bounded uncertain input disturbances. For control design it is considered a simplified mathematical model of the virus infection as a benchmark. The model is based on mass balances of healthy cells, infected cells, and the virus concentrations. The proposed controller contains a nonlinear feedback PI structure of bounded functions of the regulation error. The closed-loop stability of the system is analyzed via Lyapunov technique, in which robustness against system disturbances is demonstrated. Numerical experiments show a satisfactory performance of the proposed methodology as a HIV therapy, in which the virion particles and the infected CD4+T cells are minimized and, as an interesting result, the drug dosage can be suspended, thus avoiding drug resistance from the virus. Finally, the proposed controller is compared to a standard sliding-mode and hyperbolic tangent controllers showing better performance.

Nonlinear and Robust Control Strategy Based on Chemotherapy to Minimize the HIV Concentration in Blood Plasma

A nonlinear PI-type control strategy is designed in order to minimize the HIV concentration in blood plasma, via medical drug injection, under the framework of bounded uncertain input disturbances. For control design it is considered a simplified mathematical model of the virus infection as a benchmark. The model is based on mass balances of healthy cells, infected cells, and the virus concentrations. The proposed controller contains a nonlinear feedback PI structure of bounded functions of the regulation error. The closed-loop stability of the system is analyzed via Lyapunov technique, in which robustness against system disturbances is demonstrated. Numerical experiments show a satisfactory performance of the proposed methodology as a HIV therapy, in which the virion particles and the infected CD4+T cells are minimized and, as an interesting result, the drug dosage can be suspended, thus avoiding drug resistance from the virus. Finally, the proposed controller is compared to a standard sliding-mode and hyperbolic tangent controllers showing better performance

Sobre el comportamiento dinámico de un tipo de biorreactor con un coeficiente de rendimiento no convencional

"The goal of this work is to analyze by numerical bifurcation the dynamical behavior of a class of continuous bioreactor used to hydrolyze cellulose using Cellulomonas cellulans, talcing into account the effect of mo deling the growth rate of this microorganism by six different kinetics models (monotonic and non-monotonic). Furthermore, it is considered that the biomass yield can be modeled as a constant or a variable case, for the variable case, a substrate dependent Gaussian-type function was proposed. The proposed non-conventional yield function is a realistic appro ach that describes the behavior of the cellular yield, unlike other modelt, this one Is bounded to the maximum cellular yield and can be extrapolated to several operation conditions. Numerical results show changes in the equilibrium branches due to the kinetic growth model used. The non-conventional model of biomass yield produces a shift in the steady state multiplicity intervals, and new limit cycles were found with certain specific values of dilution rate and substrate feed.""El objetivo de este trabajo es analizar mediante bifurcation numerica el comportamiento dinámico de una clase de biorreactor continuo, utilizado para la hidrolisis de carboximetilcelulosa por Cellulomonas cellulans, tomando en cuenta el efecto de modelar la velocidad de crecimiento de este microorganismo por seis diferentes modelos cineticos no estructurados (monotonicos y no-monotónicos). En el analisis se considera que el rendimiento celular puede ser modelado como un valor constante o variable, para este ultimo caso, fue propuesta una funcion tipo Gaussiana dependiente de la concentration de sustrato. El modelo para el rendimiento celular variable utilizadorepresenta un enfoque mas realista para describir el rendimiento celular, a diferencia de otros modelos reportados, la funcion es acotada al maximo rendimiento celular y puede ser extrapolado a diferentes condiciones de operation. Los resultados numericos revelan cambios en las ramas de equilibrio debido al modelo de crecimiento utilizado. El modelo no convencional del coeficiente de rendimiento ocasiona un desplazamiento en los intervalos de multiplicidad de estados estacionarios, cambios en la estabilidad de los puntos de equilibrio y el surgimiento de ciclos límite a ciertos valores específicos de la tasa de dilution y de la concentration del sustrato de alimentation.