Exponential H∞ filtering for uncertain discrete‐time switched linear systems with average dwell time: A µ‐dependent approach

In this paper, the problem of exponential H_∞ filter problem for a class of discrete‐time polytopic uncertain switched linear systems with average dwell time switching is investigated. The exponential stability result of the general discrete‐time switched systems using a discontinuous piecewise Lyapunov function approach is first explored. Then, a new µ‐dependent approach is proposed, which means the analysis or synthesis of the underlying systems is dependent on the increase degree µ of the piecewise Lyapunov function at the switching instants. A mode‐dependent full‐order filter is designed such that the developed filter error system is robustly exponentially stable and achieves an exponential H_∞ performance. Sufficient existence conditions for the desired filter are derived and formulated in terms of a set of linear matrix inequalities, and consequently the minimal average dwell time and the corresponding filter are obtained from such conditions for a given system decay degree. A numerical example is presented to demonstrate the potential and effectiveness of the developed theoretical results. Copyright © 2007 John Wiley & Sons, Ltd.     

Simultaneous ℋ︁2/ℋ︁∞ control of uncertain jump systems with functional time‐delays

This paper presents new results pertaining to the control design of a class of linear uncertain systems with Markovian jump parameters. An integral part of the system dynamics is a delayed state in which the time‐delays are mode dependent. The jumping parameters are modelled as a continuous‐time, discrete‐state Markov process and the uncertainties are norm‐bounded. We construct an appropriate Lyapunov–Krasovskii functional and design a simultaneous ℋ︁₂/ℋ︁_∞ controller which minimizes a quadratic ℋ︁₂ performance measure while satisfying a prescribed ℋ︁_∞‐norm bound on the closed‐loop system. It is established that sufficient conditions for the existence of the simultaneous ℋ︁₂/ℋ︁_∞ controller and the associated performance upper bound are cast in the form of linear matrix inequalities. Simulation results are provided and extension to the case where the jumping rates are subject to uncertainties is presented. Copyright © 2007 John Wiley & Sons, Ltd.     

Numerical method coupling finite elements and boundary elements to model forming process tools

Nowadays, the simulation of forming process is rather well integrated in the industrial numerical codes. However, in order to take into account the possible modifications of the tool during rates of working, a dedicated numerical software is currently developed within the laboratory Roberval, this software allows to simulate forming process. The tool is discretized by boundary elements and the product, which is subjected to non-linearities, is discretized by finite elements. For the product, an isotrope law of behaviour is integrated, and the damage is taken into account by the uncoupled Rice and Tracey model. This paper deals with a contact algorithm, coupling boundary elements and finite elements, programmed in the software KSP. For that, friction is described by the Coulomb law and the resolution of contact problems is done by the penalty method. An adaptive step has been developed in order to increase the robustness of the contact algorithm.     

Harmonic elimination in diode-clamped multilevel inverter using evolutionary algorithms

This paper describes two evolutionary algorithms for the optimized harmonic stepped–waveform technique. Genetic algorithms and particle swarm optimization are applied to compute the switching angles in a three-phase seven-level inverter to produce the required fundamental voltage while, at the same time, specified harmonics are eliminated. Furthermore, these algorithms are also used to solve the starting point problem of the Newton-Raphson conventional method. This combination provides a very effective method for the harmonic elimination technique. This strategy is useful for different structures of seven-level inverters. The diode-clamped topology is considered in this study.     

Misalignment effects on steady‐state and dynamic behaviour of compliant journal bearings lubricated with couple stress fluids

This work concerns the steady‐state and dynamic analysis of misaligned compliant journal bearings considering the effects of couple stresses arising from the lubricant blended with polymer additives. Based on the Stokes micro‐continuum theory, a modified form of the Reynolds equation is derived. The displacement field at the fluid film–bearing liner interface due to pressure forces is determined using the elastic thin liner model. The effects of the misalignment and the couple stress parameters on static and dynamic performances such as pressure distribution, load‐carrying capacity, power loss, side leakage flow, misalignment moment, critical mass and whirl frequency are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Particle swarm optimization for harmonic elimination in multilevel inverters

In this paper, harmonic elimination problem in multilevel inverters with any number of levels is redrafted as an optimization task. A new method based on particle swarm optimization is proposed to identify the best switching angles with the dual objectives of harmonic suppression and output voltage regulation. The advantages of fundamental frequency harmonic elimination and swarm intelligence are combined to improve the quality of output voltage of multilevel inverters. The validity of the proposed method is proved through various simulation results.     

Erythrocyte Toxicities of Imidazolidinyl Urea and Diazolidinyl Urea

The addition of antimicrobial preservatives to pharmaceutical and cosmetic products is necessary to prevent microbial growth. However, the use of preservatives can also produce other undesirable effects. For several years, researchers have been investigating the use of alternative methods in safety assessment of cosmetic ingredients and formulations by means of variety methods. The aim of this study was to evaluate the erythrocyte toxicities of two commercial preservatives： imidazolidinyl urea and diazolidinyl urea. Relatively few studies about the cytotoxicity of these preservative are available. The determination of their cytotoxicity is an essential step to warrant their safe use. Erythrocyte toxicities were evaluated by assessment of the amount of hemoglobin released by red blood cells after their lysis. In this study, both imidazolidinyl urea and diazolidinyl urea showed cytotoxic activity against red blood cells. The imidazolidinyl urea induce a small release of hemoglobin after 120 min of incubation. But, the diazolidinyl urea induce a massive release of hemoglobin from the imidazolidinyl urea （a rate of 83% at concentrations of 6.25 mg/mL and 12.5 mg/mL）.     

Adaptive support vector machine-based surface quality evaluation and temperature monitoring. Application to billet continuous casting process

A method for surface quality evaluation and temperature monitoring of the billet in continuous casting is considered in this paper. This method uses the difference between the measured and the filtered temperature computed using an adaptive support vector machine method. The temperature field, measured by an infrared camera, is affected by an important noise called calamine (a metal oxide generated during the cooling process). The quality of the billet’s surface temperature is connected to the secondary cooling behavior, and therefore an evaluation of the calamine effect is needed. Methods such as soft sensing and adaptive support vector machine are used for a global evaluation of calamine intensity on the monitored area of the billet in continuous casting. This kind of approaches is applied in continuous casting process for constructing a complementary condition monitoring system, which allows an online calamine evaluation. Simulation results, based on the measured surface temperature and the adaptive support vector machine analysis, showed that this new combined approach is easily implementable and gives good results when applied online.