On the role of inductive loops at low frequencies in PEM electrolysis

Inductive loops at low frequencies have been observed in the electrochemical impedance spectra (EIS) of various electrochemical cells. Although different physicochemical models for this phenomenon have been suggested in many other applications, this topic has not been widely discussed in the field of proton exchange membrane (PEM) electrolysis. In this article, low-frequency inductive loops in PEM electrolysis cells and their impact on cell performance are analyzed. We show that this phenomenon is reproducible and occurs with different cell materials and setups. Its impact increases with increasing current density and decreasing temperature. At extreme conditions (7 A∙cm$^{−2}$, 40 °C) we show that the negative polarization resistance of the inductive process can exceed the capacitive polarization processes by a factor of three, resulting in a direct current resistance less than the high frequency series resistance of the cell

A Practical Approach to Gear Design and Lubrication: A Review

The modern design of mechanical parts, such as gears, goes through the continuous demand for a high level of efficiency and reliability, as well as an increased load carrying capacity and endurance life. The aim of the present paper was to perform a review and to collect practical examples in order to provide interesting tips and guidelines for gear design, including both its dimensioning and its lubrication. From this point of view, this paper is particularly novel, as it is a full-comprehensive collection of all the tools supporting gear design. Several practical aspects have been taken into account, including the definition of the right profile shifting, the selection of a proper lubricant, and the definition of the quality grade and of the tolerances needed to obtain the correct backlash. Finally, a numerical example is provided, addressing the research of the best solution to fit a given space, while maximizing the transmittable torque over weight ratio for two mating spur gears

Development of white etching bands under accelerated rolling contact fatigue

Bearing steel under severe loading condition undergoes substantial subsurface microstructural alterations known as Dark etching regions and white etching bands. White etching bands (WEBs) develop after hundreds of millions of stress cycles in bearing components and have been reported for several decades but the formation mechanism of white bands is not fully elucidated. Current research presents a systematic rolling contact fatigue (RCF) testing in a rotary tribometer under accelerated conditions, where rolling cycles are simulated in a 4-ball test configuration. The post RCF investigations have been carried out to understand the formation mechanism of WEBs in a ball-on-ball point contact load. WEBs have been characterised with the help of nanoindentation and Energy-dispersive X-ray spectroscopy analysis. The quantitative analysis of WEBs growth with subsurface stress field has revealed that the unique orientations of white bands are governed by the plane of maximum relative normal stress along the contact track. Moreover, the accelerated growth and reversal of WEBs sequence at elevated temperature have revealed that the WEBs formation is dependent on temperature/load combination. The observed growth of lenticular carbides in current research is also compared with dislocation gliding model and the role of carbon diffusion within WEBs is highlighted

Further investigations and parametric analysis of microstructural alterations under rolling contact fatigue

Bearing elements under rolling contact fatigue (RCF) exhibit microstructural features, known as white etching bands (WEBs) and dark etching regions (DERs). The formation mechanism of these microstructural features has been questionable and therefore warranted this study to gain further understanding. Current research describes mechanistic investigations of standard AISI 52100 bearing steel balls subjected to RCF testing under tempering conditions. Subsurface analyses of RCF-tested samples at tempering conditions have indicated that the microstructural alterations are progressed with subsurface yielding and primarily dominated by thermal tempering. Furthermore, bearing balls are subjected to static load tests in order to evaluate the effect of lattice deformation. It is suggested from the comparative analyses that a complete rolling sequence with non-proportional stress history is essential for the initiation and progression of WEBs, supported by the combination of carbon flux, assisted by dislocation and thermally activated carbon diffusion. These novel findings will lead to developing a contemporary and new-fangled prognostic model applied to microstructural alterations

Steuerung und Regelung des Lenkradmoments durch Nutzung radselektiver Frontantriebe

The use of wheel-individual drives on the steered axle simultaneously enables propulsion and implementation of steering assistance. This work presents a closed-loop and open-loop method for controlling wheel-selective drives with the aim of reducing the steering wheel torque. The proposed optimal linear-quadratic-integral controller achieves a high control quality while ensuring driving safety and reducing energy consumption

Steuerung und Regelung des Lenkradmoments durch Nutzung radselektiver Frontantriebe

Der Energiebedarf von Fahrzeugen ist neben dem Antriebssystem auch durch zahlreiche Unterstützungssysteme beeinflusst. Um den Energiebedarf zu senken, bietet sich daher eine funktionale Integration verschiedener Systemkomponenten an. So ermöglicht der Einsatz radselektiver Antriebe an der gelenkten Achse neben dem Vortrieb gleichzeitig die Umsetzung einer Lenkkraftunterstützung. Die vorliegende Arbeit stellt hierfür eine an Steuerungsverfahren konventioneller Lenkkraftunterstützungssysteme angelehnte Methode zur Steuerung radselektiver Antriebe mit dem Ziel einer Reduktion des Lenkradmoments vor. Des Weiteren wird ein geregeltes Verfahren zur Lenkkraftunterstützung mittels radselektiver Antriebe unter Berücksichtigung der Fahrdynamik und des Energiebedarfs dargelegt. Der entwickelte optimale linear-quadratisch-integrale Regler erreicht eine hohe Regelgüte für das Lenkradmoment bei gleichzeitiger Gewährleistung der Fahrsicherheit. Darüber hinaus kann der Energiebedarf des Fahrzeugs auch im Vergleich zu einem Fahrzeug ohne Lenkkraftunterstützung gesenkt werden. Die Validierung erfolgt hierbei sowohl simulationsbasiert als auch in der Praxis mit einem Demonstratorfahrzeug im Maßstab 1:1,5

Non-linear MPC for winding loss optimised torque control of anisotropic PMSM

For a non-linear anisotropic permanent magnet synchronous machine (PMSM), a prediction model for model predictive control (MPC) considering effects like cross-coupling and saturation is developed in a straight forward procedure. The objective of the designed MPC is either tracking of reference currents or torque tracking. Both approaches use the projected fast gradient method (PFGM) as optimisation algorithm. The latter approach makes look-up-tables for current references obsolete and additionally minimises winding losses. This two approaches are compared in a simulation study with a state of the art PI controller

Analyse der Kinematik und Kinetik von Planetenwälzgewindetrieben

Für die Umwandlung einer rotatorischen in eine translatorische Bewegung gibt es eine Vielzahl von Linearantrieben. Planetenwälzgewindetriebe (PWG) gehören zu den am besten geeigneten Antrieben für Anwendungen, die eine sehr hohe Tragfähigkeit bei maximaler Übersetzung erfordern. Kinematik und Kinetik von Planetenwälzgewindetrieben sind bisher nur punktuell zu wenigen Lastpunkten und Geometrien untersucht. Aufgrund der stark unterschiedlichen Bewegung und Freiheitsgrade der Planeten sind Erkenntnisse über Rollengewindetriebe (RGT) und Planetenrollengewindetriebe (PRGT) kaum übertragbar. Im Rahmen dieser Arbeit wird das Systemwissen über den PWG erweitert und die Auswirkungen verschiedenster Einflussfaktoren aus Anwendung und Geometrie untersucht. Einer der Schwerpunkte der Analyse ist die freie Bewegung der mit einer hohen Anzahl von Freiheitsgraden ausgestattet Planeten. Basierend auf dem Stand der Technik werden Mehrkörpersimulationen erstellt und mit Hilfe von Experimenten validiert. Mit den Simulationen wird der Einfluss verschiedenster Faktoren, wie Vorspannung und Radialspiel, auf den PWG untersucht. Nach der Analyse der Kinematik, Kinetik und der Kräfte zwischen den Körpern werden die Wälzkontakte selbst analysiert, um den Einfluss von Faktoren der Anwendung und der Geometrie zu bewerten. Schließlich werden ausgewählte Faktoren in Experimenten validiert und die Ergebnisse im Vergleich zum Stand der Technik bewertet. Die Analyse der Auswirkungen der Faktoren bis hin zu den Kontakten ermöglicht z.B. die Optimierung der Lebensdauer durch die entsprechende Einstellung der Radialluft und der Vorspannung. Darüber hinaus wird die Bedeutung der Überprüfung der Stabilität von Kräften, Bewegungen, Kontaktkräften und Kontaktpunkten für den PWG nachgewiesen - insbesondere wegen des hohen nichtlinearen Verhaltens

Diseño y construcción de un módulo para el montaje y desmontaje del rodamiento de rodillos a rótula 22208 E para el laboratorio de mantenimiento correctivo de la Facultad de Mecánica

El presente Trabajo de Integración Curricular tuvo como objetivo diseñar y construir un módulo para el montaje y desmontaje del rodamiento 22208 E de rodillos a rótula para el Laboratorio de Mantenimiento Correctivo de la Facultad de Mecánica. El desarrollo de este trabajo comprende el diseño del módulo, cálculos de cargas, selección del tipo de material, técnicas de montaje y desmontaje de rodamientos. Para la construcción del módulo se utilizó la metodología QFD, este método se encarga de recoger los requerimientos del cliente previo a su diseño y los parámetros requeridos para que funcione de manera correcta garantizando escoger la mejor alternativa antes de su construcción. Para el módulo de montaje y desmontaje de rodamientos, se diseñó cada elemento por separado, para los diferentes tipos de ejes se tomó de referencia el diámetro interno del rodamiento 22208 E, el módulo se dividió en diferentes sistemas como: estructura modular, sistema de apriete, ejes, cuerpo del hexágono, abatibles, estructura de la mesa de trabajo según la norma INEN 1641, la construcción de los elementos se realizó en dos tipos de materiales, para las estructura modular, mesa de trabajo y el cuerpo del hexágono se utilizó acero ASTM A36, para los ejes y la palanca de ajuste se mecanizó en acero de transmisión AISI 4130, para posteriormente realizar el ensamblaje mediante soldadura eléctrica. Se concluye que la metodología QFD permitió identificar la mejor alternativa de diseño antes de la construcción del módulo, la cual fue de forma ordenada y sistematizada, se realizó la práctica uno del montaje y desmontaje del rodamiento de rodillos a rotula 22208 E por el método de reducción del juego radial interno, las pruebas realizadas arrojaron un juego radial interno antes del montaje de 0,025 mm y después del montaje de 0,020 mm.This Curricular Integration Project aims to design and construct a module for assembling and disassembling a spherical roller bearing, specifically the 22208 E model, for the Corrective Maintenance Laboratory of the Faculty of Mechanical Engineering. This technical project includes the module's design, load calculations, selection of materials, and techniques for bearing assembly and disassembly. The QFD methodology was used for module construction. It involves gathering customer requirements prior to design and determining the necessary parameters for its correct functioning, ensuring the selection of the best alternative before construction. For the assembly and disassembly module, each element was individually designed. The internal diameter of the 22208 E bearing served as a reference for different types of shafts. The module was divided into various systems, including the modular structure, clamping system, shafts, hexagonal body, foldable components, and workbench structure according to the INEN 1641 standard. Two materials were used for construction: ASTM A36 steel for the modular design, workbench, and hexagonal body, and AISI 4130 transmission steel for the shafts and adjustment lever. Assembly was carried out through electric welding. In conclusion, the QFD methodology allowed for identifying the best design alternative before module construction, ensuring an organized and systematic approach. The assembly and disassembly practice for the 22208 E spherical roller bearing was conducted using the method of reducing internal radial clearance. The tests yielded a pre-assembly internal radial clearance of 0.025 mm, which was reduced to 0.020 mm after assembly

Harmonic current injection for torque ripple reduction with optimum current trajectory for minimum induced voltage

Electric drives often do not have a smooth torque. In most cases they are coupled with mechanical systems. These tend to have natural frequencies. Therefore, it is advisable to eliminate harmonics from the torque pulsation if they are close to a natural frequency. One possibility to do this is harmonic current injection or HCI for short. However, the question arises, how exactly this harmonic current should be. The fact that a harmonic in the torque can be influenced by the d and q current results in a greater degree of freedom. This paper presents a method to investigate all possible solutions. Furthermore, two optimization possibilities for the current trajectory are presented. The effect of this selection on the maximum torque speed curve is shown. It has been found that the method which minimizes the induced voltage achieves an up to 8% larger range of application in this example