Ricardo Femat

Fuzzy-Based Controller for Glucose Regulation in Type-1 Diabetic Patients by Subcutaneous Route

This paper presents an advisory/control algorithm for a type-1 diabetes mellitus (TIDM) patient under an intensive insulin treatment based on a multiple daily injections regimen (MDIR). The advisory/control algorithm incorporates expert knowledge about the treatment of this disease by using Mamdani-type fuzzy logic controllers to regulate the blood glucose level (BGL). The overall control strategy is based on a two-loop feedback strategy to overcome the variability in the glucose-insulin dynamics from patient to patient. An inner-loop provides the amount of both rapid/short and intermediate/long acting insulin (RSAI and ILAI) formulations that are programmed in a three-shots daily basis before meals. The combined preparation is then injected by the patient through a subcutaneous route. Meanwhile, an outer-loop adjusts the maximum amounts of insulin provided to the patient in a time-scale of days. The outer-loop controller aims to work as a supervisor of the inner-loop controller. Extensive closed-loop simulations are illustrated, using a detailed compartmental model of the insulin-glucose dynamics in a TIDM patient with meal intake

A chaos-based communication scheme via robust asymptotic feedback

A communication scheme based on chaos synchronization via feedback is presented. The main idea is to construct an augmented dynamical system from the synchronization error system, which is itself uncertain. Dynamic output feedback is applied to perform synchronization in spite of transmitter/receiver mismatches. In this way, the transmitted message (which can be analog or digital) can be recovered. Two illustrative examples are presented. (1) The Chua oscillator is used to show that the message signal is recovered in spite of parametric transmitter/receiver mismatches. (2) Two second-order driven oscillators are presented to show that the message can be recovered in spite of a strictly different model, which results in different master/slave dynamics.

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.

An extension to chaos control via Lie derivatives: Fully linearizable systems

The technique of using Lie derivatives to control chaos introduced by Kocarev et al. [Chaos, Solitons Fractals 9, 1359-1366 (1998)] is extended in this contribution. Here, by using Lie derivatives in an extended space state, it is proved that chaos can be practically suppressed via feedback in spite of the Lie derivative being ill-posed at the reference. The main idea is to construct a dynamically equivalent system. In this way, the chaotic system can be practically stabilized around any point of singularity x(0). The Lorenz equation is used as an illustrative example to show the application in the chaos control context. (c) 2002 American Institute of Physics.

Knowledge-based controllers for blood glucose regulation in Type I diabetic patients by subcutaneous route

This paper presents the design methodology for Mamdani-type fuzzy logic controllers to regulate the blood glucose level in a Type I diabetic patient. The overall control strategy is based on a two-loop feedback strategy. The inner-loop provides the amount of both rapid (Lispro) and slow (NPH) insulin types that the patient has to program in a three-shoots daily basis. The combined preparation is then injected to the patient through a subcutaneous route. Meanwhile, the outer-loop adjusts the maximum amounts of insulin provided to the patient. In this way, it is pursued to optimize the amount of insulin required to maintain a normal glucose level. Both controllers were synthesized gathering information about physician treatment of diabetic patients using fuzzy logic.

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.

On the dynamic optimization of methane production in anaerobic digestion via extremum-seeking control approach

This paper proposes an extremum-seeking control approach based on sliding mode to achieve the dynamic optimization of methane outflow rate in anaerobic digestion processes. Open-loop analysis for a two-population model shown that the system becomes unstable due at the accumulation of volatile fatty acids (VFA). Then the controller is designed to achieve the regulation of VFA concentration close to the optimal set-point while maximizing the methane production. The control law is based on a variable-structure feedback to iteratively extremize the methane outflow rate and converges to the neighborhood of the optimum with sliding mode motions. In contrast with previous works on extremum-seeking control with sliding mode, the control scheme includes an observer-based uncertain estimator which computes the unknown terms related to the growth kinetics and the inlet composition. Practical stabilizability for the closed-loop system around to unknown optimal set-point is analyzed. Numerical experiments illustrate the effectiveness of the proposed approach.

A note on robust stability analysis of chaos synchronization

Robust stability analysis of a class of synchronized systems is addressed in this work. The problem is focused departing from the µ-analysis of the H∞ control theory. Main question is, if two chaotic systems behave in synchronous way, how stable is the synchronized behavior? A quantitative measure of the robustness margin of the chaotic synchronization is studied in this work. The class of synchronized systems comprises second-order driven oscillators. An illustrative example shows the results of the robustness issues on the chaotic synchronization.  2001 Elsevier Science B.V. All rights reserved.

On dynamical behaviour of two-dimensional biological reactors

The dynamical behaviour for a generic two-dimensional model of a continuous bioreactor is studied in this article. The state variables for the bio-reacting system are restricted to concentrations of substrate and biomass, where the specific growth rate is a smooth function of the substrate concentration, which can be a kinetic function, monotone or non-monotone (as Monod, Haldane, Teissier, etc.). The effect of input (dilution rate) on multiplicity and bifurcation of equilibrium is shown in open-loop configuration. The absence of limit cycles on open-loop configuration and through state-feedback on the dilution rate are demonstrated. The aim of analysing oscillations under state feedback control is related to the possible improvement of reactor yields under this operation regime. An example for a cell-producing bioreactor illustrates the analytical results.

Analog Electronic Implementation of a Class of Hybrid Dissipative Dynamical System

An analog electronic implementation by means of operational amplifiers of a class of hybrid dissipative systems in R3 is presented. The switching systems have two unstable hyperbolic focus-saddle equilibria with the same stability index, a positive real eigenvalue and a pair of complex conjugated eigenvalues with negative real part. The analog circuit generates signals that oscillate in an attractor located between the two unstable equilibria, and may present saturation states at the moment of energizing it, i.e. if the initial voltage on the capacitors do not belong to the basin of attraction the circuit will end on a saturation state.