Hector Puebla

Chaos control using small-amplitude damping signals

The aim of this Letter is to show that the injection of small damping signals can suffice to regulate the motion of a chaotic system around less complex attractors, such as equilibrium points and periodic orbits. The proposed feedback controller is composed by a high-pass filter and a saturator, so its implementation is quite simple and can be made on the basis of measured signals. The Duffing and the Chua systems are used to illustrate the performance of the controller.

Linear boundary control for a class of nonlinear PDE processes

Abstract This paper studies the problem of output regulation via boundary feedback control for a class of nonlinear PDE processes, including important industrial (bio)-chemical reactors. Under physically reasonable smoothness, stability and steady-state assumptions, it is proven that a linear stable controller with integral action yields global exponential regulation of the process output.

Removal of Cr(VI) from wastewaters at semi-industrial electrochemical reactors with rotating ring electrodes.

In Mexico, most of the electroplating and textile industries are small facilities and release relatively large amounts of hexavalent chromium (Cr(VI)) in surface waters. In this work, the results obtained during the operation of a batch reactor with a capacity of 170 L, and three electrochemical flow reactors-in-series system with a total capacity of 510 L (both using iron rotating ring electrodes to remove Cr(VI) from wastewaters) are presented. The reactors were scaled up from a laboratory reactor to a semi-industrial level, based on the similarity (dynamical, geometrical and electrochemical). An empirical Cr(VI) removal model was validated in batch and continuous reactors at different operating conditions. Cr(VI) concentration of the industrial wastewaters was reduced from about 500 mg/L to values lower than 0.5mg/L. A very important parameter that affects the process is the pH, which affects the solubility of the Fe(III). Finally, the electrochemical treated wastewater can be reused.

More secure communication using chained chaotic oscillators

Abstract In this Letter, a strategy for more secure communication using chaotic signals is presented. In this approach, the transmitter is composed by a chain of chaotic oscillator where the input to the first oscillator is modulated by the information signal and the transmitted signal is the output of the last oscillator. The receiver is a linear asymptotic approximation to the inverse of the transmitter system and contains an integral feedback to cope with nonlinearities and parameter variations. The functioning of the information encoding/decoding system is illustrated with a cascade of colpitts and Chuas circuits.

A Cascade Control Approach for a Class of Biomedical Systems

An approach for the robust feedback control of a class of biomedical systems in chained form is presented. The control approach is based on modeling error compensation techniques and a recursive cascade scheme. Numerical simulations on three biomedical models of VIH-1, cancer and glucose systems are provided to illustrate our findings

A Cascade Feedback Control Approach for Hypnosis

This article studies the problem of controlling the drug administration during an anesthesia process, where muscle relaxation, analgesia, and hypnosis are regulated by means of monitored administration of specific drugs. On the basis of a seventh-order nonlinear pharmacokinetic-pharmacodynamic representation of the hypnosis process dynamics, a cascade (master/slave) feedback control structure for controlling the bispectral index (BIS) is proposed. The master controller compares the measured BIS with its reference value to provide the expired isoflurane concentration reference to the slave controller. In turn, the slave controller manipulates the anesthetic isoflurane concentration entering the anesthetic system to achieve the reference from the master controller. The advantage of the proposed cascade control structure with respect to its noncascade counterpart is that the former provides operation protection against BIS measurement failures. In fact, under a BIS measurement fault, the master control feedback is broken and the slave controller operates under a safe reference value. Extensive numerical simulations are used to illustrate the functioning of the proposed cascade control structure.

Monitoring anaerobic sequential batch reactors via fractal analysis of pH time series

Efficient monitoring and control schemes are mandatory in the current operation of biological wastewater treatment plants because they must accomplish more demanding environmental policies. This fact is of particular interest in anaerobic digestion processes where the availability of accurate, inexpensive, and suitable sensors for the on‐line monitoring of key process variables remains an open problem nowadays. In particular, this problem is more challenging when dealing with batch processes where the monitoring strategy has to be performed in finite time, which limits the application of current advanced monitoring schemes as those based in the proposal of nonlinear observers (i.e., software sensors). In this article, a fractal time series analysis of pH fluctuations in an anaerobic sequential batch reactor (AnSBR) used for the treatment of tequila vinasses is presented. Results indicated that conventional on‐line pH measurements can be correlated with off‐line determined key process variables, such as COD, VFA and biogas production via some fractality indexes. Biotechnol. Bioeng. 2013; 110: 2131–2139.

An Integral High-Order Sliding Mode Control Approach for Stick-Slip Suppression in Oil Drillstrings

Abstract In this paper a novel sliding mode control law combined with a cascade control scheme is proposed for the suppression of stick-slip oscillations in oil drillstrings. It is assumed that the parameters of the system are uncertain and external disturbances are present. Numerical simulations on a generic simple model of stick-slip oscillations are provided to illustrate the control performance.

A simple tracking control for Chua's circuit

This brief addresses the problem of designing a robust tracking controller for a nonlinear Chuas circuit involving plant uncertainties and external disturbances. Given a bounded desired trajectory, a robust tracking controller, which is based on modeling-error compensation is developed such that all the states and signals of the closed-loop system are bounded and the tracking error can be made as small as desired. In contrast to the previous proposed controllers for tracking control of Chuas circuit, the controller developed here is linear and equivalent to a traditional PI compensator.

Convergence rate of observer-based approach for chaotic synchronization

Abstract The aim of this Letter is to characterize a class of nonlinear system for which the observer gain can be given explicitly and the convergence rate of the synchronization error can be arbitrarily assigned.