Flat connection for rotating vacuum spacetimes in extended teleparallel gravity theories

Teleparallel geometry utilizes Weitzenb\"ock connection which has nontrivial torsion but no curvature and does not directly follow from the metric like Levi-Civita connection. In extended teleparallel theories, for instance in $f(T)$ or scalar-torsion gravity, the connection must obey its antisymmetric field equations. So far only a few analytic solutions were known. In this note we solve the $f(T,\phi)$ gravity antisymmetric vacuum field equations for a generic rotating tetrad ansatz in Weyl canonical coordinates, and find the corresponding spin connection coefficients. By a coordinate transformation we present the solution also in Boyer-Lindquist coordinates, often used to study rotating solutions in general relativity. The result hints for the existence of another branch of rotating solutions besides the Kerr family in extended teleparallel gravities.Comment: minor clarifications and references added; 14 pages, no figures; contributed to the special issue "Selected Papers from Teleparallel Universes in Salamanca 2018

Full- & Reduced-Order State-Space Modeling of Wind Turbine Systems with Permanent-Magnet Synchronous Generator

Wind energy is an integral part of nowadays energy supply and one of the fastest growing sources of electricity in the world today. Accurate models for wind energy conversion systems (WECSs) are of key interest for the analysis and control design of present and future energy systems. Existing control-oriented WECSs models are subject to unstructured simplifications, which have not been discussed in literature so far. Thus, this technical note presents are thorough derivation of a physical state-space model for permanent magnet synchronous generator WECSs. The physical model considers all dynamic effects that significantly influence the system's power output, including the switching of the power electronics. Alternatively, the model is formulated in the $(a,b,c)$- and $(d,q)$-reference frame. Secondly, a complete control and operation management system for the wind regimes II and III and the transition between the regimes is presented. The control takes practical effects such as input saturation and integral windup into account. Thirdly, by a structured model reduction procedure, two state-space models of WECS with reduced complexity are derived: a non-switching model and a non-switching reduced-order model. The validity of the models is illustrated and compared through a numerical simulation study.Comment: 23 pages, 11 figure

Explicit Port-Hamiltonian Representation of Feedthrough-Systems with Nonlinear Dissipation

In this technical note, we present an explicit port-Hamiltonian formulation of feedthrough systems subject to nonlinear energy-dissipating effects. To this end, we merge the Dirac structure which describes the system\u27s internal interconnection structure with the constitutive relations of energy-storing and energy-dissipating elements. The resulting port-Hamiltonian system (PHS) is proven to be passive and generalizes an existing nonlinear-dissipative port-Hamiltonian formulation from the literature by feedthrough

MSCAN als Methode zur Bestimmung der Anzahl motorischer Einheiten bei Patienten mit Amyotropher Lateralsklerose

ALS ist eine neurodegenerative Erkrankung mit kombinierter Affektion der oberen und unteren Motoneurone, wodurch es zur Überlagerung der Symptomatik kommt. Ziel dieser Arbeit war es, das neue Verfahren Muscle Scan (MSCAN) als Messmethode der Anzahl motorischer Einheiten in der Routinearbeit der neuromuskulären Ambulanz zu etablieren. Darüber hinaus galt es zu testen, inwieweit sich MSCAN zur Diagnosestellung und Verlaufsbeobachtung der ALS sowie des für diese Krankheit typischen Split-Hand-Syndroms eignet. MSCAN beruht auf dem Prinzip des Threshold Tracking und nutzt natürliche Schwankungen axonaler Erregbarkeit zur exakten Quantifizierung der motorischen Einheiten. Zudem erlaubt es Aussagen über die Zusammensetzung des Compound Muscle Action Potential (CMAP) und liefert weitere Informationen über einzelne Einheiten. Die Ergebnisse der Messungen wurden mit gleichzeitig erhobenen klinischen Parametern verglichen. Dabei spielte insbesondere das D50-Progressionsmodell eine wichtige Rolle, welches anhand des Funktionsverlustes eine Einteilung der Krankheit in Phasen erlaubt. Messungen wurden bei 39 ALS-Patienten sowie 19 gesunden Kontrollen an zwei Handmuskeln (APB, ADM) sowie einem Beinmuskel (TA) durchgeführt. Verlaufsmessungen wurden nach 5-7 Monaten bei 20 Patienten und nach 10-14 Monaten bei 12 Patienten durchgeführt. Die Anzahl motorischer Einheiten sowie das CMAP waren bei ALS-Patienten im Vergleich zu gesunden Kontrollen in allen drei Muskeln signifikant reduziert. Sowohl CMAP als auch motorische Einheiten nahmen im Verlauf ab, wenngleich hier keine Signifikanz nachgewiesen werden konnte. Zusammen mit dem D50-Progressionsmodell konnte gezeigt werden, dass in allen Muskeln die Anzahl motorischer Einheiten im Vergleich zu gesunden Kontrollen bereits in Phase I der Erkrankung signifikant geringer war. Zudem konnte bei Patienten ein signifikant geringeres APB/ADM-Verhältnis als Hinweis auf das Split-Hand-Syndrom nachgewiesen werden

Distributed and Decentralized Kalman Filtering for Cascaded Fractional Order Systems

This paper presents a distributed Kalman filter algorithm for cascaded systems of fractional order. Certain conditions are introduced under which a division of a fractional system into cascaded subsystems is possible. A functional distribution of a large scale system and of the state estimation algorithm leads to smaller and scalable nodes with reduced memory and computational effort. Since each subsystem performs its calculations locally, a central processing node is not needed. All data which are required by subsequent nodes are communicated to them unidirectionally. Also a comparison between the Fractional Kalman Filter (FKF) and the Cascaded Fractional Kalman Filter (CFKF) is given by an example

Full-Order Observer Design for a Class of Nonlinear Port-Hamiltonian Systems

In this paper, we present a simple method to design a full-order observer for a class of nonlinear port-Hamiltonian systems (PHSs). We provide a sufficient condition for the observer to be globally exponentially convergent. This condition exploits the natural damping of the system. The observer and its design are illustrated by means of an academic example system. Numerical simulations verify the convergence of the reconstructions towards the unknown system variables

Full-Order Observer Design for a Class of Nonlinear Port-Hamiltonian Systems

In this paper, we present a simple method to design a full-order observer for a class of nonlinear port-Hamiltonian systems (PHSs). We provide a sufficient condition for the observer to be globally exponentially convergent. This condition exploits the natural damping of the system. The observer and its design are illustrated by means of an academic example system. Numerical simulations verify the convergence of the reconstructions towards the unknown system variables