Performance measures in the genetic design of digital controllers for robotic manipulators

Genetic algorithms are used to design digital multivariable PID controllers for robotic manipulators for typical trajectory-tracking tasks when various different performance measures are used. It is thus shown that, by using an appropriate performance measure, the set of controller parameters can be readily found that determines the optimal time-domain trajectory-tracking behaviour for such tasks. This use of genetic algorithms is illustrated by the design of digital trajectory-tracking PID controllers for a typical three-degree-of-freedom robotic manipulator.published_or_final_versio

Genetic robustification of digital trajectory: tracking controllers for robotic manipulators

In this paper, genetic algorithms are used to robustify digital multivariable PID controllers for robotic manipulators. This process of robustification is effected by using genetic algorithms to determine the optimal set of controller tuning parameters for typical trajectory-tracking tasks. This use of genetic algorithms is illustrated by the design of a digital trajectory-tracking controller for a typical three-degree-of-freedom robotic manipulator.published_or_final_versio

Evolutionary design of digital trajectory-tracking controllers for robotic manipulators

The design of digital trajectory-tracking controllers for robotic manipulators is a challenging task, since such manipulators are multivariable non-linear plants. In addition, in many applications of robotic manipulators, it is required that very high-accuracy trajectory-tracking performance be achievable even in the presence of unpredictable payload variations. These requirements can all be met to some extent by application of the previously developed fast-sampling digital PID controllers to robotic manipulators. Indeed, for such controllers, it is possible to prove a series of very reassuring robustness results using only the Markov parameters associated with locally linearised representations of robotic manipulators.However, these theoretical optimisation results for digital PID controllers are only valid as sampling periods become vanishingly small. In practice, of course, the sampling periods of digital controllers remain non-zero; but, in such cases, no theoretical optimisation results are available. There is, therefore, a great need for some alternative optimisation procedure that will facilitate the non- asymptotic design of digital PID controllers for robotic manipulators.This design need is addressed in this thesis. In particular, the following evolutionary optimisation techniques are used to design digital trajectorytracking controllers for robotic manipulators:(i) genetic algorithms,(ii) non-adaptive evolution strategies(iii) adaptive evolution strategies.It is shown that, with increasing effectiveness, these techniques are very useful in the design of high-accuracy digital PID controllers. These techniques are illustrated by the presentation of simulation results for a typical three-link robotic manipulator performing a range of demanding trajectory-tracking tasks in the presence of unpredictable payload variations. In addition, these evolutionary optimisation techniques are also used in the design of unconstrained digital PID controllers, in which all elements of the controller matrices are used as the design parameters.In order to validate these evolutionary design techniques in practice, an experimental laboratory investigation is also undertaken. This involves the practical implementation, in the case of a direct-drive two-link robotic manipulator, of digital PID trajectory-tracking controllers designed using evolutionary techniques. The results thus obtained indicate that such optimisation techniques greatly facilitate the tuning of digital PID controllers for robotic manipulators under practical non-asymptotic conditions

Fenugreek proteins and their hydrolysates prevent hypercholesterolemia and enhance the HDL antioxidant properties in rats

Purpose This paper aims to investigate the in vivo hypocholesterolemic property of fenugreek proteins (FP), Purafect-fenugreek protein hydrolysate (PFPH) and Esperase-fenugreek protein hydrolysate (EFPH) on high cholesterol (HC)-fed rats. Design/methodology/approach Rats were randomized into five groups: four were fed for four weeks a hypercholesterolemic diet and the tested products were given by gavage. The fifth group was taken as control (C) receiving the same diet without cholesterol. Findings Results showed that the elevated aspartate aminotransferase activity in HC group plasma was significantly corrected by FP and EFPH administration (-33 per cent; p = 0.0003). HC liver lipids and total cholesterol (TC) contents were not markedly affected by FP and EFPH. However, liver triglycerides (TG) contents trended to decrease in FP rats vs HC (p = 0.07), while, the TG decrease was significant in groups fed the proteins hydrolysates (p = 0.02). On the other hand, serum TC and TG decreased by 53 per cent (p = 0.0003) and 20 per cent (p = 0.04), respectively, in FP treated rats compared to HC group. This decrease was associated with a high fecal cholesterol excretion (2.5-fold higher in FP vs HC; p = 0.0001). Likewise, EFPH-treated rats exhibited lower TC compared to HC rats (p = 0.004). The very low density lipoprotins was the main affected fraction in these two groups, while there were no significant difference in apolipoproteins (Apo) B, A-I and A-IV contents between the different groups, except in FP group, where Apo A-I and A-IV decreased by 26 and 17 per cent, respectively, compared to C rats (p = 0.02). The high density lipoproteins (HDL) of rats treated with proteins hydrolysates showed a better antioxidant property compared to those of HC rats, which was accompanied with an increase in paraoxonase activity when compared to HC group. Originality/value Unlike PFPH which had almost no effect, FPs and EFPH could constitute a nutraceutical ingredient in cardiovascular disease management

Gradually decreasing daylength after smoltification induced by “winter signal“ reduced sexual maturation in male Atlantic salmon

publishedVersio

Characterization of the Promoter, MxiE Box and 5′ UTR of Genes Controlled by the Activity of the Type III Secretion Apparatus in Shigella flexneri

Activation of the type III secretion apparatus (T3SA) of Shigella flexneri, upon contact of the bacteria with host cells, and its deregulation, as in ipaB mutants, specifically increases transcription of a set of effector-encoding genes controlled by MxiE, an activator of the AraC family, and IpgC, the chaperone of the IpaB and IpaC translocators. Thirteen genes carried by the virulence plasmid (ospB, ospC1, ospD2, ospD3, ospE1, ospE2, ospF, ospG, virA, ipaH1.4, ipaH4.5, ipaH7.8 and ipaH9.8) and five genes carried by the chromosome (ipaHa-e) are regulated by the T3SA activity. A conserved 17-bp MxiE box is present 5′ of most of these genes. To characterize the promoter activity of these MxiE box-containing regions, similar ∼67-bp DNA fragments encompassing the MxiE box of 14 MxiE-regulated genes were cloned 5′ of lacZ in a promoter probe plasmid; β-galactosidase activity detected in wild-type and ipaB strains harboring these plasmids indicated that most MxiE box-carrying regions contain a promoter regulated by the T3SA activity and that the relative strengths of these promoters cover an eight-fold range. The various MxiE boxes exhibiting up to three differences as compared to the MxiE box consensus sequence were introduced into the ipaH9.8 promoter without affecting its activity, suggesting that they are equally efficient in promoter activation. In contrast, all nucleotides conserved among MxiE boxes were found to be involved in MxiE-dependent promoter activity. In addition, we present evidence that the 5′ UTRs of four MxiE-regulated genes enhance expression of the downstream gene, presumably by preventing degradation of the mRNA, and the 5′ UTRs of two other genes carry an ancillary promoter

Histone Methylation by NUE, a Novel Nuclear Effector of the Intracellular Pathogen Chlamydia trachomatis

Sequence analysis of the genome of the strict intracellular pathogen Chlamydia trachomatis revealed the presence of a SET domain containing protein, proteins that primarily function as histone methyltransferases. In these studies, we demonstrated secretion of this protein via a type III secretion mechanism. During infection, the protein is translocated to the host cell nucleus and associates with chromatin. We therefore named the protein nuclear effector (NUE). Expression of NUE in mammalian cells by transfection reconstituted nuclear targeting and chromatin association. In vitro methylation assays confirmed NUE is a histone methyltransferase that targets histones H2B, H3 and H4 and itself (automethylation). Mutants deficient in automethylation demonstrated diminished activity towards histones suggesting automethylation functions to enhance enzymatic activity. Thus, NUE is secreted by Chlamydia, translocates to the host cell nucleus and has enzymatic activity towards eukaryotic substrates. This work is the first description of a bacterial effector that directly targets mammalian histones