A necessary and sufficient condition for total observability of discrete-time linear time-varying systems

This paper deals with the total observability problem of discrete-time linear time-varying systems. In particular, a review and suitable analysis of the state-of-the-art of this emerging area are provided. Subsequently, the total observability problem of discrete-time linear time-varying systems is transformed into the one of checking the rank of a convex sum of matrices. As a result, a new total observability test is proposed, along with a suitable computational strategy. The final part of this paper shows examples regarding observability analysis that clearly exhibit the benefits of using the proposed approach.Postprint (published version

A practical test for assessing the reachability of discrete-time Takagi-Sugeno fuzzy systems

This paper provides a necessary and sufficient condition for the reachability of discrete-time Takagi-Sugeno fuzzy systems that is easy to apply, such that it constitutes a practical test. The proposed procedure is based on checking if all the principal minors associated to an appropriate matrix are positive. If this condition holds, then the rank of the reachability matrix associated to the Takagi-Sugeno fuzzy system is full for any possible sequence of premise variables, and thus the system is completely state reachable. On the other hand, if the principal minors are not positive, the property of the matrix being a block P one with respect to a particular partition of a set of integers is studied in order to conclude about the reachability of the Takagi-Sugeno system. Examples obtained using an inverted pendulum are used to show that it is easy to check this condition, such that the teachability analysis can be performed efficiently using the proposed approach.This paper provides a necessary and sufficient condition for the reachability of discrete-time Takagi-Sugeno fuzzy systems that is easy to apply, such that it constitutes a practical test. The proposed procedure is based on checking if all the principal minors associated to an appropriate matrix are positive. If this condition holds, then the rank of the reachability matrix associated to the Takagi-Sugeno fuzzy system is full for any possible sequence of premise variables, and thus the system is completely state reachable. On the other hand, if the principal minors are not positive, the property of the matrix being a block P one with respect to a particular partition of a set of integers is studied in order to conclude about the reachability of the Takagi-Sugeno system. Examples obtained using an inverted pendulum are used to show that it is easy to check this condition, such that the teachability analysis can be performed efficiently using the proposed approach.Postprint (author's final draft

The impact of chronic alcohol overuse on heart function and prognosis: layer-specific longitudinal strain and mid-term outcome analysis

Background: The exact effects of alcohol drinking on cardiac function are not clear.Aims: This study aimed to determine the relationship between consumed amount of alcohol, myocardial injury, and prognosis.Methods: Myocardial function and cardiac outcomes were examined in subjects with chronic alcoholism by classical and strain echocardiographic parameters, including global (GLS) and layer-specific longitudinal strain of the endocardial (GLSendo) and epicardial (GLSepi) layer. One group of 65 alcohol-overusers (ALC), median (IQR, interquartile range) age 44 (38–51) years, was compared with 30 controls (CG).Results: Median (IQR) alcohol dose (in alcohol units, 1 AU = 1 g of ethanol) per week was 30 (12–51) AU in ALC and 0 in CG; P <0.001, and the mean (SD, standard deviation) drinking period was 16 (9) years. ALC patients demonstrated higher left ventricular (LV) mass and impaired diastolic function. The ALC group demonstrated lower median (IQR) LV ejection fraction (EF): 52% (37%–57%) vs 60% (55%–63%) (P <0.001); GLS: 17% (9%–20%) vs 19% (18%–21%) (P = 0.01); absolute layer-specific strain values. GLSendo <19% and GLSepi <15% predicted worsened mid-term prognosis, as did elevated N-terminal brain natriuretic peptide (NT-proBNP) and lower EF and GLS.Conclusions: Long-term alcohol overuse, even with a rather low reported median (IQR) dose of 4 (2–7) AU per day resulted in LV hypertrophy, diastolic and systolic dysfunction. Diminished GLS <18%, endocardial <19% and epicardial <15% layer strain predicted combined endpoints but did not significantly improve the prognostic power of tested models, based on NT-proBNP and EF in follow-up

A predictive actuator fault-tolerant control strategy under input and state constraints

International audienceThe paper deals with the design of a robust predictive fault-tolerant control for linear discrete-time systems with an applicationof the quadratic boundedness theory and an associated robust invariant set. The main problem is to maintain the state of thesystem inside the robust invariant set obtained under asymmetric input and state constraints. The proposed strategy relies on athree-stage procedure, which is based on adaptive fault estimation as well as robust and predictive controller. The fault-recovery procedure is initiated with fault estimation and then the fault is compensated with a robust controller. In a case when robust fault compensation fails, i.e. the current state does not belong to the robust invariant set, a suitable predictive action is started. The main goal of this action is to generate control allocation enhancing the robust invariant set. This appealing phenomenon makes it possible to enlarge the domain of attraction of the possibly faulty system. The final part of the paper shows an illustrative example regarding a two-tank system

Analysis of Core Losses in Transformer Working at Static Var Compensator

This article presents the comparison of 3D and 2D finite element models of a power transformer designed for reactive power compensation stations. There is a lack of studies in the literature on internal electromagnetic phenomena in the active part of a transformer operated in these conditions. The results of numerical 2D and 3D calculations of no-load current and losses in the transformer core were obtained by using various methods and models. The impact of considering the hysteresis loop phenomenon on the calculation of core losses was investigated by using the Jiles–Atherton core losses model. The results obtained in the paper show that the model of the core must contain the areas representing the influence of overlappings on the no-load current and also on the flux density field in the core. The capacitive load of the transformer increases the flux density in the core limbs by several percent, so the power losses there must also increase accordingly. As a summary of the research, differences in the values of losses in each core element between the capacitive load and no-load conditions are presented. The results presented in this paper indicate that considering nonlinearity related to the magnetic hysteresis loop has a significant impact on the calculation of the core losses of power transformers

A necessary and sufficient condition for total observability of discrete-time linear time-varying systems

This paper deals with the total observability problem of discrete-time linear time-varying systems. In particular, a review and suitable analysis of the state-of-the-art of this emerging area are provided. Subsequently, the total observability problem of discrete-time linear time-varying systems is transformed into the one of checking the rank of a convex sum of matrices. As a result, a new total observability test is proposed, along with a suitable computational strategy. The final part of this paper shows examples regarding observability analysis that clearly exhibit the benefits of using the proposed approach.Peer Reviewe

A necessary and sufficient condition for total observability of discrete-time linear time-varying systems

This paper deals with the total observability problem of discrete-time linear time-varying systems. In particular, a review and suitable analysis of the state-of-the-art of this emerging area are provided. Subsequently, the total observability problem of discrete-time linear time-varying systems is transformed into the one of checking the rank of a convex sum of matrices. As a result, a new total observability test is proposed, along with a suitable computational strategy. The final part of this paper shows examples regarding observability analysis that clearly exhibit the benefits of using the proposed approach