Robust fuzzy PSS design using ABC

This paper presents an Artificial Bee Colony (ABC) algorithm to tune optimal rule-base of a Fuzzy Power System Stabilizer (FPSS) which leads to damp low frequency oscillation following disturbances in power systems. Thus, extraction of an appropriate set of rules or selection of an optimal set of rules from the set of possible rules is an important and essential step toward the design of any successful fuzzy logic controller. Consequently, in this paper, an ABC based rule generation method is proposed for automated fuzzy PSS design to improve power system stability and reduce the design effort. The effectiveness of the proposed method is demonstrated on a 3-machine 9-bus standard power system in comparison with the Genetic Algorithm based tuned FPSS under different loading condition through ITAE performance indices

genetisch programmeren en codegroei

De complexiteit van de problemen waarmee een ingenieur heden in contact komt, neemt steeds toe. Hierdoor wordt de verleiding om een aantal concepten uit de biologie te lenen en zo het probleemoplossend vermogen van de ingenieur aan te scherpen, groter. Reeds vanaf 1960 probeert men computationele systemen te ontwerpen volgens de principes van Charles Darwin. Genetisch programmeren is zo een dergelijke evolutionaire optimalisatiemethode voor het automatisch creëren van computerprogramma's. Echter, wanneer genetisch programmeren wordt gebruikt om steeds complexere taken op te lossen, vertonen deze programma’s een steeds sterker wordende drang om te groeien (codegroei). Het doel van dit werk is de bestrijding van codegroei in al zijn facetten. Het eerste deel van dit werk omvat de ontwikkeling van een nieuwe methode om codegroei te bestrijden zonder de kwaliteit van de geëvolueerde computerprogramma's negatief te beïnvloeden. Deze methode gaat op zoek naar geschikte deelprogramma’s waarbij aan een aantal voorwaarden moet worden voldaan. Een tweede luik van dit werk bestaat uit de ontwikkeling van adaptieve methoden om codegroei te bestrijden. Deze sturingsalgoritmen hebben als primair doel de instellingen voor de gebruiker te beperken en te vereenvoudigen alsook om probleemafhankelijkheden weg te werken. Dankzij codegroei hebben programma's de neiging om overgespecialiseerd te raken. In het derde deel ontwikkelen we een strategie om nieuwe testvoorbeelden aan te maken. We evalueren tevens de invloed die de nieuw ontwikkelde codegroei begrenzer uitoefent op de robuustheid van de bekomen oplossingen

Influence of dexamethasone and gamithromycin on the acute phase response in LPS-challenged calves

Introduction : Lipopolysaccharide (LPS) is a potent inducer of the bovine acute phase response and has been widely used in research to provoke acute inflammation. An intravenous challenge with LPS elicits the endogenous synthesis and release of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). These cytokines initiate fever and stimulate the hepatic production of acute phase proteins, such as Serum Amyloid A (SAA). Regarding the fact that immunomodulating drugs are able to influence this acute phase response, the aim of the present research was to study the potentials of dexamethasone and gamithromycin in a standardized LPS-inflammation model. Dexamethasone was applied as a positive control, due to its major anti-inflammatory effects. The novel azalide gamithromycin on the other hand, was selected since macrolide antibiotics have been reported to exert immunomodulatory effects. Furthermore, the combination of both drugs was studied for possible additive and/or synergistic effects. Materials and Methods : A standardized and reproducible inflammation model was developed by challenging twelve 4-week-old calves intravenously with a single dose of LPS (E. coli serotype O111:B4, 0.5 µg/kg body weight (BW)). Three control animals on the other hand received an equivalent volume of 0.9% NaCl. Rectal body temperature was measured and plasma samples were collected at several points in time until 72h p.a. These samples were analyzed using ELISAs for TNF-α, IL-6 and SAA. As part of the immunomodulation study, eighteen different calves were randomly divided in three groups, each group consisting of six calves. The groups received a single bolus of respectively 0.3 mg/kg BW dexamethasone i.m. (Dexa 0.2%®, Kela), 6 mg/kg BW gamithromycin s.c. (Zactran®, Merial) and the combination of both drugs. At Tmax of the drug (time at which the maximum plasma concentration is reached) the LPS-bolus was administered, followed by a similar experimental design as for the inflammation model. Results and Conclusions : In comparison with the results obtained in LPS-administered animals which did not receive any treatment, dexamethasone and the combination of dexamethasone and gamithromycin significantly inhibited the release of TNF-α, IL-6 and SAA after an LPS-challenge. The administration of gamithromycin solely did not affect the cytokine and acute phase protein concentrations. Regarding the course of the body temperature, neither dexamethasone, nor the combination had a major influence, while gamithromycin alone induced a remarkable delay of the maximum body temperature. In other words, these results demonstrate the possible additive effect of a combined administration of an antibiotic with a corticosteroid in the acute phase of a bacterial infection, which could contribute to a better clinical condition of the animal

Switched predictive control design for optimal wet-clutch engagement

Modeling of hydraulic clutch transmissions is far from straightforward due to their nonlinear hybrid dynamics, i.e. switching between three dynamic phases. In this paper we identify a local linear model only for the constrained first phase, based on which a predictive controller is used to track a suitable engagement signal. The robustness of this controller in the latter two phases is guaranteed by making the constraints inactive and pre-tuning the control parameters based on its closed loop formulation and applying robust stability theorem. This controller is then implemented in real-time on a wet-clutch test setup and is shown to achieve optimal engagement