Cross Feedback Control of a Magnetic Bearing System: Controller Design Considering Gyroscopic Effects

For flywheel rotors or other rotors with significant ratios of moments of inertia, the influence of gyroscopic effects has to be considered. While conservative or damped systems remain stable even under gyroscopic effects, magnetically suspended rotors can be destabilized with increasing rotational speed. The influence of gyroscopic effects on the stability and behavior of a magnetic bearing system is analyzed. The analysis is carried out with a rigid body model for the rotor and a nonlinear model for the magnetic bearing and its amplifier. Cross feedback control can compensate gyroscopic effects. This compensation leads to better system performance and can avoid instability. Furthermore, the implementation of this compensation is simple. The main structure of a decentralized controller can still be used. It has only to be expanded by the cross feedback path

A Model for Axial Magnetic Bearings Including Eddy Currents

This paper presents an analytical method of modelling eddy currents inside axial bearings. The problem is solved by dividing an axial bearing into elementary geometric forms, solving the Maxwell equations for these simplified geometries, defining boundary conditions and combining the geometries. The final result is an analytical solution for the flux, from which the impedance and the force of an axial bearing can be derived. Several impedance measurements have shown that the analytical solution can fit the measured data with a precision of approximately 5%

Aktive, modellbasierte Verschleißbeeinflussung beim Außenrundeinstechschleifen mittels elektromagnetischer Aktoren

Als geometrisch unbestimmtes Bearbeitungsverfahren stellt das Schleifen einen abschließenden und qualitätsbestimmenden Fertigungsschritt dar. Im Prozess auftretende Schwingungen, wie sie beispielsweise durch den Regenerativeffekt verursacht werden, können die Prozesssicherheit und die Werkstückqualität deutlich senken. Dabei treten insbesondere in Rundschleifprozessen mit konventionellen Schleifmitteln (\zB Korund, Siliziumkarbid) selbsterregte, produktivitätsbegrenzende Schwingungen auf. Diese entstehen durch die Wechselwirkung zwischen dem Prozess und der dynamischen Nachgiebigkeit von Schleifmaschine und Werkstück. Schwingungen, hervorgerufen durch Welligkeiten auf dem Werkstück, kommen in Rundschleifprozessen nur in sehr niedrigen Frequenzbereichen vor und können deshalb durch passende Wahl der Prozessstellgrößen vermieden werden. Hingegen können Schwingungen, die zu einer Konturänderung der Schleifscheibe führen, in hohen Frequenzbereichen auftreten. Der vorgenannte Regenerativeffekt entsteht, verglichen mit dem werkstückseitigen Regenerativeffekt, langsam und führt erst nach längerem Fortschritt zu einer Reduktion der Oberflächenqualität des Werkstücks. Die Prognose und Vermeidung dieses werkzeugseitigen Regenerativeffektes stellt die Fertigung dennoch vor große Herausforderungen und kann nur durch häufige Abrichtzyklen oder reduzierte Zeitspanvolumina vermieden werden, was jedoch die Produktivität vermindert. Da das Schleifen am Ende der Wertschöpfungskette angesiedelt ist, kommt dem frühzeitigen Erkennen von regenerativen Prozessschwingungen eine besondere Bedeutung zu, um Ausschuss zu vermeiden und Durchlaufzeiten zu verringern. In dieser Arbeit werden Methoden zur frühzeitigen Erkennung dieser Schwingungen entwickelt und untersucht, welche die Realisierung von teil- oder vollautomatisierten Schleifprozessen ermöglichen. Darüber hinaus soll der Regenerativeffekt mithilfe einer modellbasierten Verschleißregelung und elektromagnetischer Aktoren derart beeinflusst werden, dass eine Bildung von Welligkeiten auf der Schleifscheibe vermieden wird.Using conventional grinding wheels (corundum, silicon carbite), one of the most limiting factors in terms of productivity and process stability in cylindrical plunge grinding are self-excited vibrations. These vibrations are caused by regenerative effects during the process and can reduce productivity and workpiece quality. Workpiece oscillations induced by single grain-workpiece contacts and limited dynamic stiffness of the grinding machine copy on the grinding wheel surface. This results in a regenerative effect, where a further increasing waviness of the grinding wheel causes an increasing workpiece vibration. While the regenerative effect can also develop on the surface of the workpiece, the resulting frequencies are much higher when appearing on the grinding wheel surface. Thus, they are much more difficult to manage and put high requirements on process planning and demand for frequent trueing operations and reduced feed rates. In scope of this work, the development and evaluation of methods for early chatter detection is presented. Since the progress of the waviness on the grinding wheels surface progresses relatively slowly, it is possible to manipulate the process forces in an early stage of chatter development. Dynamic process forces applied to the workpiece by electromagnetic actuators are capable of influencing the workpiece movement and therefore, the wear. Hence, the development of wheel-sided chatter vibration caused by waves on the grinding wheel can be prevented. This ensures a chatter free, stable grinding process

Faster Goal-Oriented Shortest Path Search for Bulk and Incremental Detailed Routing

We develop new algorithmic techniques for VLSI detailed routing. First, we improve the goal-oriented version of Dijkstra's algorithm to find shortest paths in huge incomplete grid graphs with edge costs depending on the direction and the layer, and possibly on rectangular regions. We devise estimates of the distance to the targets that offer better trade-offs between running time and quality than previously known methods, leading to an overall speed-up. Second, we combine the advantages of the two classical detailed routing approaches - global shortest path search and track assignment with local corrections - by treating input wires (such as the output of track assignment) as reservations that can be used at a discount by the respective net. We show how to implement this new approach efficiently

Spectroscopic and redox properties of amine-unctionalized K_2[Os-^(II)(bpy)(CN)_4] complexes

We report the first examples of amine-functionalized K_2[Os^(II)(bpy)(CN)_4] (bpy = 2,2'-bipyridine) complexes. The tetracyanoosmate complexes were prepared by UV irradiation (λ = 254 nm) of K_4[Os^(II)(CN)_6] and primary amine-functionalized bpy ligands in acidic aqueous media. The aqueous solution pH dependences of the spectroscopic and redox properties of 4,4'- and 5,5'-substituted complexes have been investigated. The pendant amine functional groups and coordinated cyanide ligands are basic sites that can be sequentially protonated, thereby allowing systematic tuning of electrochemical and optical spectroscopic properties

Global apparent temperature sensitivity of terrestrial carbon turnover modulated by hydrometeorological factors

We are in debt to FLUXNET principal investigators and researchers for the fundamental measurements and synthesis datasets used to build the upscaled and in situ flux datasets used in this study. The work used eddy covariance data from La Thuile Synthesis Dataset, which were provided by the FLUXNET community. In particular, we thank A. Altaf, J. Beringer, P. Blanken, C. Brümmer, S. Burns, J. Cleverly, E. Cremonese, T. Grünwald, P. Kolari, W. Jans, M. Leonardo, T. Manise, M. Mund, A. Noormets, E. Pendall, C. Pio, S. Prober, L. Šigut, A. Varlagin and W. Woodgate, who provided us with site-level measurements of soil carbon and vegetation biomass, and B. Amiro, J. Ardö, S. Arndt, D. Baldocchi, L. Belelli, F. Bosveld, D. Bowling, N. Buchmann, A. Christen, M. Cuntz, A. Desai, B. Drake, I. Goded, A. Goldstein, C. Gough, S. Ivan, L. Hutley, I. Janssens, M. Karan, H. Kobayashi, M. Korkiakoski, B. Kruijt, S. Linder, B. Loubet, I. Mammarella, S. Minerbi, W. Munger, Z. Nagy, D. Papale, A. Richardson, B. Ruiz, E.P. Sanchez-Canete, FCE. Silva, E. Veenendaal, S. Wharton, G. Wohlfahrt, J. Wood, D. Yakir and D. Zona, who provided contacts and/or references for us to find site-level measurements of soil carbon and vegetation biomass. We are thankful to S. Bao and S. Besnard for helping with collected and processed site-level FLUXNET and vegetation biomass data. We thank M. Migliavacca and M. Schrumpf for providing reference and useful resources for data collection. N.F. acknowledges support from the International Max Planck Research School for Global Biogeochemical Cycles. Publisher Copyright: © 2022, The Author(s).The ecosystem carbon turnover time—an emergent ecosystem property that partly determines the feedback between the terrestrial carbon cycle and climate—is strongly controlled by temperature. However, it remains uncertain to what extent hydrometeorological conditions may influence the apparent temperature sensitivity of τ, defined as the factor by which the carbon turnover time increases with a 10 °C rise in temperature (Q10). Here, we investigate the responses of the ecosystem carbon turnover to temperature and hydrometeorological factors using an ensemble of observation-based global datasets and a global compilation of in situ measurements. We find that temperature and hydrometeorology are almost equally important in shaping the spatial pattern of ecosystem carbon turnover, explaining 60 and 40% of the global variability, respectively. Accounting for hydrometeorological effects puts a strong constraint on Q10 values with a substantial reduction in magnitude and uncertainties, leading Q10 to converge to 1.6 ± 0.1 globally. These findings suggest that hydrometeorological conditions modulate the apparent temperature sensitivity of terrestrial carbon turnover times, confounding the role of temperature in quantifying the response of the carbon cycle to climate change.publishersversionpublishe

Survey about the dissemination of different cabin categories in plant protection of German practice

Das Bundesamt für Verbraucherschutz und Lebensmittelsicherheit (BVL) hat festgelegt, dass bestimmte Fahrerkabinen beim Einsatz im Pflanzenschutz geeignet sind, persönliche Schutzausrüstung zu ersetzen, die mit der Zulassung von Pflanzenschutzmitteln während der Anwendung vorgeschrieben sind. Diese Schutzwirkung wird seit 2017 für Fahrerkabinen der Kategorien 3 oder 4 (EN 15695-1/2017) und seit 2020 für geschlossene Kabinen, die über eine Klimaanlage sowie eine Zuluft-Filterung verfügen (BVL-Kategorie 2*), angenommen. Das Schutzniveau von Kat. 2* Kabinen wird aktuell in einem Forschungsprojekt untersucht.Vor diesem Hintergrund wurde eine Umfrage bei Praktikern durchgeführt, um mehr Informationen über die Verbreitung und Ausstattung von Traktorkabinen in der landwirtschaftlichen Praxis in Deutschland zu erhalten.Der Fragebogen gliedert sich in zwei Abschnitte. Im ersten Teil werden demografische Daten zur Person sowie Daten zur Struktur und Lage des Betriebs erfasst. Im zweiten Teil geht es um die technische Ausstattung und Nutzung der Fahrzeuge. Insgesamt konnten 4.199 gültige Fragebögen ausgewertet werden. Die Ergebnisse aus Teil 1 der Umfrage zur prozentualen Verteilung der beteiligten Betriebe über die Bundesländer und die repräsentierten Betriebsgrößen sind nahe an den statistischen Daten von Destatis. Größere Betriebe sind in dieser Umfrage leicht überrepräsentiert. Trotzdem liefern die Ergebnisse profunde Informationen über die Verbreitung von verschiedenen Kabinenkategorien in der landwirtschaftlichen Praxis im Pflanzenschutz in Deutschland.Die Auswertung zeigt, dass es in den letzten 10 Jahren zu einer signifikanten Zunahme von Kabinen der Kategorie 3 und 4 in der Praxis gekommen ist, mit einem etwas höheren Anteil bei den größeren Betrieben. In Bezug auf die Betriebsform ist der Anteil von Kategorie 3 und 4 Kabinen insbesondere im Obstbau, in den Spezialkulturen und bei den Lohnunternehmen höher. Die Umfrage lieferte weitere Ergebnisse, unabhängig von der Kabinenkategorie. Es zeigte sich, dass das Wechselintervall bei den Zuluft-Filtern in den meisten Fällen kleiner als 2 Jahre ist, dass 40% der Befragten angeben, ihre Kabinen nach der Applikation von Pflanzenschutzmitteln zu reinigen und knapp 90% der Anwender sich in ihrer Kabine gut gegen Pflanzenschutzmittel geschützt fühlen. Die Ergebnisse sind plausibel und decken sich mit früheren Annahmen. Mit der Veröffentlichung der Ergebnisse liegen jetzt stichhaltige Informationen zu diesem Thema vor.The Federal Office of Consumer Protection and Food Safety (BVL) specified that certain driver cabs are suitable to replace personal protective equipment prescribed with the approval of plant protection products during application. This protective effect has been accepted since 2017 for category 3 or 4 driver's cabs (EN 15695-1/2017) and since 2020 for enclosed cabs equipped with air conditioning including an air filtration system (BVL category 2*). The protection level of cat. 2* cabins is currently being investigated in a research project. In this context, a survey of farmers was conducted to obtain more information about the distribution and equipment of tractor cabins in agricultural practice in Germany. The questionnaire is divided into two sections. The first part collects personal demographic data and data on the structure and location of the farms. The second part deals with the technical equipment and use of the vehicles. A total of 4,199 valid questionnaires were evaluated. The results from Part 1 of the survey on the percentage distribution of participating farms across the German Federal States and the sizes of farms represented are close to the statistical data from Destatis. Larger farms are slightly overrepresented in this survey. Nevertheless, the results provide profound information on the prevalence of different cab categories in agricultural practice in plant protection in Germany.The survey provided further results, regardless of the cab category. It showed that the replacement interval for cabin air filters is less than 2 years in most cases, that 40% of the participants indicated that they clean their cab after applying plant protection products, and that almost 90% of the users feel well protected against plant protection products in their cab. The results are plausible and in line with earlier assumptions. With the publication of the results, valid information on this topic is now available

Vertically divergent responses of SOC decomposition to soil moisture in a changing climate

The role of soil moisture for organic matter decomposition rates remains poorly understood and underrepresented in Earth System Models (ESMs). We apply the Dual Arrhenius Michaelis-Menten (DAMM) model to a selection of ESM soil temperature and moisture outputs to investigate their effects on decomposition rates, at different soil depths, for a historical period and a future climate period. Our key finding is that the inclusion of soil moisture controls has diverging effects on both the speed and direction of projected decomposition rates (up to ± 20%), compared to a temperature-only approach. In the top soil, the majority of these changes is driven by substrate availability. In deeper soil layers, oxygen availability plays a relatively stronger role. Owing to these different moisture controls along the soil depth, our study highlights the need for depth-resolved inclusion of soil moisture effects on decomposition rates within ESMs. This is particularly important for C-rich soils in regions which may be subject to strong future warming and vertically opposing moisture changes, such as the peat soils at northern high latitudes.Vertically divergent responses of SOC decomposition to soil moisture in a changing climatepublishedVersio

Enabling Logic Computation Between Ta/CoFeB/MgO Nanomagnets

Dipolar coupled magnets proved to have the potential to be capable of successfully performing digital computation in a highly parallel way. For that, nanomagnet-based computation requires precise control of the domain wall nucleation from a well-localized region of the magnet. Co/Pt and Co/Ni multilayer stacks were successfully used to demonstrate a variety of computing devices. However, Ta/CoFeB/MgO appears more promising, thanks to the lower switching field required to achieve a full magnetization reversal, reduced thickness (less than 10 nm), and its compatibility with magnetic tunnel junctions. In this work, the switch of the information is achieved through the application of a magnetic field, which allows to scale more the nanomagnets with respect to current-driven magnetization reversal-based devices and to go toward 3-D structures. We experimentally demonstrate that Ga ions can be used to tune the energy landscape of the structured magnets to provide signal directionality and achieve a distinct logic computation. We prove that it is possible to define the artificial nucleation center (ANC) in different structures with two irradiation steps and that this approach can enable logic computation in ultrathin films by dipolar interaction. Moreover, different from previous studies, the results coming from the irradiation analysis are then used for real logic devices. We present the experimental demonstration of a set of fully working planar inverters, showing that it is possible to reach a coupling field between the input and the output, which is strong enough to reliably implement logic operations. Micromagnetic simulations are used to study the nucleation center's effectiveness with respect to its position in the magnet and to support the experiments. Our results open the path to the development of more efficient nanomagnet-based logic circuits