A robust multivariable control for an electropneumatic system using backstepping design

International audienceDuring the last twenty years, the parallel development of pneumatic systems and control theory has lead to the implementation of modern control laws in pneumatic devices. This paper deals with the robust control problem of a pneumatic actuator subjected to mass flow leakage inside the servodistributor and load disturbances. The control strategy is based on backstepping design. For this, backstepping is presented in an informal setting. The nonlinear model of the electropneumatic system is presented. This one is transformed to be nonlinear affine model and a coordinate transformation is then related to make possible the implementation of the nonlinear controller. Control laws are developed using backstepping design to control position and pressure. The robustness visa -vis modeling errors and some unknown terms is proved. Finally, the experiment results are presented and discussed

Investigating Mutations to Reduce Huntingtin Aggregation by Increasing Htt-N-Terminal Stability and Weakening Interactions with PolyQ Domain

Huntington’s disease is a fatal autosomal genetic disorder characterized by an expanded glutamine-coding CAG repeat sequence in the huntingtin (Htt) exon 1 gene. The Htt protein associated with the disease misfolds into toxic oligomers and aggregate fibril structures. Competing models for the misfolding and aggregation phenomena have suggested the role of the Htt-N-terminal region and the CAG trinucleotide repeats (polyQ domain) in affecting aggregation propensities and misfolding. In particular, one model suggests a correlation between structural stability and the emergence of toxic oligomers, whereas a second model proposes that molecular interactions with the extended polyQ domain increase aggregation propensity. In this paper, we computationally explore the potential to reduce Htt aggregation by addressing the aggregation causes outlined in both models. We investigate the mutation landscape of the Htt-N-terminal region and explore amino acid residue mutations that affect its structural stability and hydrophobic interactions with the polyQ domain. Out of the millions of 3-point mutation combinations that we explored, the (L4K E12K K15E) was the most promising mutation combination that addressed aggregation causes in both models. The mutant structure exhibited extreme alpha-helical stability, low amyloidogenicity potential, a hydrophobic residue replacement, and removal of a solvent-inaccessible intermolecular side chain that assists oligomerization

Design of a compliant positioning control using an inverse method

International audienceThe design of new system requires generally achieving different objectives. The choice of the right system and control architecture is crucial and they can be judiciously exploited. The proposed approach is dealing with the efficient use of a pneumatic cylinder controlled by two servovalves. The control objectives are independent position and stiffness tracking. A Bond graph approach gives, in a first step, a general methodology to check the accessibility of the specifications on energetic and dynamic criteria. Then a control algorithm issued from the flatness concept and the nonlinear control theory is developed. Simulation and experimental results illustrating the proposed principle are finally presented. Concerning the tracking performance, it is shown that the new strategy does not decrease tracking errors, or the static errors, or the standard deviation in term of position and velocity tracking. The performance of the stiffness control is finally illustrated in simulation

A solution to the stick slip problem for an electropneumatic drive

International audienceThis paper describes a solution to the problem of "stick-slip" for an electro-pneumatic system. The phenomenon of "stick-slip" may appear during the mechanical static state when the position is fixed but the pressures continue to evolve in each actuator chamber, until exceeding the dry friction zone. The system is then in partial equilibrium. The idea to avoid this phenomenon is a switching control law between the tracking position control and the pressure regulation

Near-infrared spectrometry in pregnancy: progress and perspectives, a review of literature

Near-infrared spectroscopy (NIRS) allows continuous noninvasive monitoring of in vivo oxygenation in selected tissues. It has been used primarily as a research tool for several years, but it is seeing wider application in the clinical arena all over the world. It was recently used to monitor brain circulation in cardiac surgery, carotid endarteriectomy, neurosurgery and robotic surgery. According to the few studies used NIRS in pregnancy, it may be helpful to assess the impact of severe forms of preeclampsia on brain circulation, to evaluate the  efficacy of different treatments. It may also be used during cesarean section to detect earlier sudden  complications. The evaluation of placental function via abdominal maternal approach to detect fetal growth restriction is a new field of application of NIRS.Key words: Near-Infrared Spectrometry, pregnancy, preeclamsia, cesarean sectio

Change of Diet, Plasma Lipids, Lipoproteins, and Fatty Acids during Ramadan: A Controversial Association of the Considered Ramadan Model with Atherosclerosis Risk

Different Islamic populations have different alimentary habits, notably during Ramadan. The paper reports the change of diet, lipids, and lipoproteins produced during Ramadan in one Tunisian population. During Ramadan, the study subjects consumed more proteins, cholesterol, vitamin E (p<0.01), and polyunsaturated fatty acids (p<0.05). At the same time, they exhibited an increase in total cholesterol, low-density lipoprotein-cholesterol (p<0.01) and apoprotein B (p<0.05) and a decrease in the ratio of apoprotein AI to apoprotein B (p<0.01). All assayed saturated fatty acids were unaffected by Ramadan fasting while three unsaturated fatty acids (C18:1cis9, C18:2n-6, and C30:4n-6) increased significantly. A return to the habitual diet for a four-week period was not sufficient to restore the pre-fasting patterns. For the study subjects, Ramadan was clearly associated with a change of diet and biochemical profile but its effective impact on atherosclerosis risk was unclear, perhaps, because other non-alimentary changes ought to be considered too. Future studies considering the non-alimentary factors, such as sleep and physical activity, would be useful to clarify the contribution of dietary change in the observed modification of biological profile

Réhabilitation précoce post césarienne: enquête de pratique auprès des maternités de la région de Sfax en Tunisie

Introduction: Bien que la plupart des principes de réhabilitation précoce post césarienne paraissent applicable dans nos structures de soins, il semble que la mise en oeuvre reste limitée. Méthodes: Il s'agit d'une enquête structurée par courrier électronique auprès des médecins anesthésistes de la région de Sfax décrivant leurs pratiques habituelles dans les maternités étatiques et privées de la région de Sfax. Nous avons utilisé un questionnaire dans le cadre de prise en charge de la césarienne programmée. Résultats: Le taux de réponse des médecins était de 68% (30/44). L'analgésie orale a été débutée au cours des 24 premières heures par 13% des anesthésistes. La perfusion post opératoire a été arrêtée avant 24h dans 27% des cas. Le Retrait de la sonde &lt; H6, la reprise des boissons &lt; H6, la reprise de l'alimentation &lt; H12 ont été observé respectivement dans 57%, 63% et 30% des cas. L'emploi d'ocytocine limité à H6 est la conduite de 60% des médecins interrogés. La carbétocine est encore non utilisée. Conclusion: Les différents composants de la réhabilitation précoce post césarienne sont encore insuffisamment mis en oeuvre.Pan African Medical Journal 2016; 2

0106: Association of lipoproteina and cholesteryl ester transfer protein-TaqIB polymorphism in Tunisian type 2 diabetes

Lipoprotein (a) [Lp(a)] is a plasma lipoprotein consisting of a LDL-like particle with a molecule of apolipoprotein B100 covalently linked to a very large additional glycoprotein known as apolipoprotein(a). Elevated Lp(a) levels constitute an independent risk factor for cardiovascular disease in the general population. Several studies have examined the possibility that type 2 diabetes could influence Lp(a) concentrations. Cholesteryl ester transfer protein (CETP) plays a key role in lipoprotein metabolism, promoting the exchange of triglycerides (TGs) and cholesteryl esters (CEs) between lipoprotein particles. The CETP TaqIB polymorphism in type 2 diabetes may have an increased risk for coronary artery disease.The aim of the present study was to examine the effect of the genetic polymorphism TaqIB of the CETP on the Lp(a) concentrations and the risk of coronaropathy in a cohort of type 2 diabetes.Plasma Lp(a) levels are not significantly associated with CETP TaqIB polymorphism in type 2 diabetes: no significant difference in the plasma Lp (a) between the diabetics having the genotype B1B1 and those having the genotype B2 (365.8±259 vs. 317±250.1mg; p=0.20). For the diabetics with genotype B1B1, Lp (a) was correlated significantly with the LDL (n=90, r=0.32; p=0.002) and the apoB (n=90, r=0.24, p=0.01). The proportion of the diabetics having the allèle B2 and Lp (a) superior to 300mg/l, is clearly more important at those having coronaropathy (51.1 vs. 29.2%; odds ratio=2.53; p=0.03).Lp(a) levels is a risk factor for cardiovascular disease in type 2 diabetic patients. This atherogenic risk seems to depend on the genetic polymorphism TaqIB of the CETP

Nonlinear force tracking control of electrohydrostatic actuators submitted to motion disturbances

In some industrial fields, such as aerospace, electro-hydrostatic actuators (EHAs) are increasingly used to replace conventional standard hydraulic actuators due to their better energy performance. Moreover, implementing different type or technology of actuators in redundant actuation systems working on the same moving part introduced some new challenges. This paper presents a force-tracking controller for an asymmetric electro-hydrostatic actuator that is submitted to an external motion generated by an external source. In this case, the rod displacement is considered as an external disturbance for the hydraulic cylinder, but it is assumed that this disturbance can be easily measured using sensors. The theoretical motivation of this work is discussed along and a variable gain state feedback control based on Linear Parameter Varying control (LPV) theory is proposed to achieve stability, disturbance rejection and tracking performance. The Linear Matrix Inequalities (LMI) framework is used to determine a control law including an augmented state feedback with an integral action that reduces trajectory-tracking errors. Simulation results of the control law are finally given to verify the global performance of this control design