7 research outputs found
Robust design of standard controllers under plant parameters uncertainty
No full textThis note extends some results concerning the characterization of PID and lead/lag controllers satisfying given H-infinity closed–loop
specifications. In particular, it is shown that: (i) the region of the plane of the free controller parameters where the considered H-infinity constraint is satisfied, is still formed by the union of (a bounded number of) disjoint convex sets even
when the plant parameters are not fixed but belong to given intervals, and
(ii) the determination of these sets entails the repeated solution of an optimization problem. The procedure is applied to find the parameters of a PID
controller for an uncertain electric motor so as to ensure that the H1 norm
of the sensitivity function is less than a prescribed value
Input/output decoupling of Boolean control networks
No full textIn this study, the author investigates the input/output decoupling problem for Boolean control networks (BCNs). To keep up with the spirit of the original definition for linear state-space models, that pertains the relationship between inputs and outputs independently of the state variables, two properties that formalise in different ways the idea that each single component of the output depends on the values of the corresponding input are provided, but not on the values of the other inputs. These properties are introduced by referring to the classical representation of a BCN in terms of Boolean input, state and output vectors, whose mutual relationships are expressed through the logical operators AND, OR and so on. In this set-up, it is proven that there is some natural ordering among these properties, namely that one of them implies the other. In the second part of this study, it is shown that by resorting to the algebraic representation of BCNs a complete characterisation of these properties is possible. The algebraic characterisations obtained through this approach provide easy to check algorithms to evaluate whether a BCN is input/output decoupled or not. Finally, graph-theoretic characterisations of the two input/output decoupling properties are provided
Identification of structured LTI MIMO state-space models
No full textThe identification of structured state-space model has been intensively studied for a long time but still has not been adequately addressed. The main challenge is that the involved estimation problem is a non-convex (or bilinear) optimization problem. This paper is devoted to developing an identificationmethod which aims to find the global optimal solution under mild computational burden. Key to the developed identification algorithm is to transform a bilinear estimation to a rank constrained optimization problem and further a difference of convex programming (DCP) problem. The initial conditionfor the DCP problem is obtained by solving its convex part of the optimization problem which happens to be a nuclear norm regularized optimization problem. Since the nuclear norm regularized optimization is the closest convex form of the low-rank constrained estimation problem, the obtained initialcondition is always of high quality which provides the DCP problem a good starting point. The DCP problem is then solved by the sequential convex programming method. Finally, numerical examples are included to show the effectiveness of the developed identification algorithm.Accepted Author ManuscriptApplied MechanicsTeam Michel Verhaege
Cardiomyopathy and sudden cardiac death: bridging clinical practice with cutting-edge research
No full textSudden cardiac death (SCD) prevention in cardiomyopathies such as hypertrophic (HCM), dilated (DCM), non-dilated left ventricular (NDLCM), and arrhythmogenic right ventricular car- diomyopathy (ARVC) remains a crucial but complex clinical challenge, especially among younger populations. Accurate risk stratification is hampered by the variability in phenotypic expression and genetic heterogeneity inherent in these conditions. This article explores the multifaceted strategies for preventing SCD across a spectrum of cardiomyopathies and emphasizes the integration of clinical evaluations, genetic insights, and advanced imaging techniques such as cardiac magnetic resonance (CMR) in assessing SCD risks. Advanced imaging, particularly CMR, not only enhances our under- standing of myocardial architecture but also serves as a cornerstone for identifying at-risk patients. The integration of new research findings with current practices is essential for advancing patient care and improving survival rates among those at the highest risk of SCD. This review calls for ongoing research to refine risk stratification models and enhance the predictive accuracy of both clinical and imaging techniques in the management of cardiomyopathies
Functional T-observers
No full textAbstractThis article is a contribution to behavioral observer theory which was started by Valcher and Willems in 1999 and which was recently exposed by Fuhrmann in a comprehensive survey article. It is also a further development of the article on T-observers by Oberst and the author. For a given continuous or discrete time linear time-invariant behavior we assume that a linear function of a trajectory (e.g., some components) can be measured. We are interested in estimating another linear function of this trajectory.We generalize the notions of T-observability and T-observers introduced by Oberst and the author. T denotes a multiplicatively closed subset of the ring of operators. For different choices of T,T-observability coincides with observability, reconstructibility, trackability, or detectability, a T-observer is an exact, dead-beat, tracking, or asymptotic observer. We show the equivalence of T-observability and the existence of T-observers and give a constructive parametrization of all T-observers. Corresponding results for proper T-observers are also presented.Partial observation of the state of a Kalman state space system (compare e.g. Fuhrmann’s work) is a special case of our setting, and so are the observers of certain unknown components of a behavior studied by Bisiacco, Valcher, and Willems. The first result on functional observers in context with Rosenbrock equations or polynomial matrix descriptions is due to Wolovich (1974)
Low-voltage area ablation in addition to pulmonary vein isolation in patients with atrial fibrillation: a systematic review and meta-analysis
No full textBackground: Low-voltage area (LVA) ablation, in addition to pulmonary vein isolation (PVI), has been proposed as a new strategy in patients with atrial fibrillation (AF), but clinical trials have shown conflicting results. We performed a systematic review and meta-analysis to assess the impact of LVA ablation in patient undergoing AF ablation (PROSPERO-registered CRD42024537696). Methods: Randomized clinical trials investigating the role of LVA ablation in addition to PVI in patients with AF were searched on PubMed, Embase, and the Cochrane Library from inception to 22 April 2024. Primary outcome was atrial arrhythmia recurrence after the first AF ablation procedure. Secondary endpoints included procedure time, fluoroscopy time, and procedure-related complication rate. Sensitivity analysis including only patients with LVA demonstration at mapping and multiple subgroups analyses were also performed. Results: 1547 patients from 7 studies were included. LVA ablation in addition to PVI reduced atrial arrhythmia recurrence (odds ratio [OR] 0.65, 95% confidence interval [CI] 0.52-0.81, p < 0.001) with a number needed to treat to prevent recurrence of 10. No difference in procedure time (mean difference [MD] -5.32 min, 95% CI -19.01-8.46 min, p = 0.45), fluoroscopy time (MD -1.10 min, 95% CI -2.48-0.28 min, p = 0.12) and complication rate (OR 0.81, 95% CI 0.40-1.61, p = 0.54) was observed. Consistent results were demonstrated when considering only patients with LVA during mapping and in prespecified subgroups for AF type (paroxysmal vs. persistent), multicentric vs. monocentric trial, and ablation strategy in control group. Conclusions: In patients with AF, ablation of LVAs in addition to PVI reduces atrial arrhythmia recurrence without a significant increase in procedure time, fluoroscopy time, or complication rate
Myocardial work parameters in left bundle branch area pacing versus other pacing techniques: a systematic review and aggregate comparative analysis
No full textCardiac conduction disease often necessitates permanent pacemaker implantation. While right ventricular pacing (RVP) effectively treats bradycardia, it may lead to adverse cardiac remodeling and heart failure. Left bundle branch area pacing (LBBAP) has emerged as an alternative, potentially preserving myocardial function. Non-invasive myocardial work (MW) assessment provides valuable insights into left ventricular systolic function, energetics, and efficiency. This study systematically reviewed and analyzed MW parameters, comparing LBBAP to RVP and His bundle pacing (HBP). A meta-analysis of 241 patients across five studies examined four MW parameters—Global Work Index (GWI), Global Constructive Work (GCW), Global Wasted Work (GWW), and Global Work Efficiency (GWE)—at baseline, post-implantation, and last follow-up (median: 180 days, IQR: 7–360 days). At baseline, MW parameters were similar between LBBAP and RVP. Post-implantation, LBBAP preserved MW more effectively, showing significantly higher GWI than RVP (2250.0 ± 400.0 vs. 1600.0 ± 300.0 mmHg%, p = 0.027), a difference that remained significant at follow-up (p = 0.035). GWE was also significantly higher at follow-up (p = 0.011), while GCW and GWW showed no significant differences. MW parameters did not differ significantly between LBBAP and HBP (all p-values >0.05). These findings suggest that LBBAP provides superior MW preservation compared to RVP, with significant benefits in GWI and GWE, while demonstrating comparable performance to HBP
