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Die Analyse der geometrischen Parameter der Werkzeuge und der kinematisch bedingten Eingriffsverhältnisse beim Fräsen führen zu einer erheblichen Beeinflussung der Schneidenbelastungen während des Einsatzes. Eine exzentrische Aufnahme von Schaftwerkzeugen bedeutet eine deutliche Belastung der exzentrischen Schneiden. Diese Belastung liegt deutlich über der durch die Ungleichteilung erzeugten Kraftmodulation. Weiterhin werden durch die Impulsbelastung der Schneideneintritte die Resonanzen der Struktur angeregt. Dies beeinflusst zum einen die Messungen mit der Kraftmessplattform. Zum anderen werden während der realen Bearbeitung durch diese Wechselwirkung die Oberflächen der bearbeiteten Bauteile beeinflusst.
At higher frequencies the triaxial cell becomes in principle a cavity resonator which shows different resonance frequencies depending on the dimensions of the cell as well as on the size of the DUT. Above these resonance frequencies propagation of TEM waves is disturbed and measurements of screening attenuation with triaxial test method according to IEC 62153-4-15 are limited. Higher order modes respectively resonance frequencies can be suppressed by using conductive absorber material such as ferrites, nanocrystalline absorbers, magnetic absorbers or foam absorbers, placed in the Triaxial cell. With these absorbers, the frequency range of the screening attenuation measured in Triaxial cell can be extended up to several GHz.
Ein praktikables Mittel zur Erhöhung des Automatisierungsgrads im analogen IC-Entwurf ist die Verwendung parametrisierter Zellen. Diese sogenannten pCells werden eingesetzt, um determinierte Layouts automatisch zu erzeugen, und zwar in der Regel für einzelne Bauelemente wie Transistoren oder Dioden. Der vorliegende Beitrag zeigt die Potenziale eines erweiterten pCell-Konzepts, mit dem determinierte Layouts als auch Schaltpläne für ganze Schaltungsmodule automatisch generiert werden können. Als Beispiel wird eine solche Modul-pCell für analoge Stromspiegel beschrieben, die nicht nur die Dimensionierung der Einzeltransistoren, sondern auch verschiedene Transistortypen, beliebige Spiegelverhältnisse und sogar mehrere Topologien sowie weitere Freiheitsgrade implementiert. Das dadurch erzielte Maß an Flexibilität erlaubt es, die zahlreichen schaltungstechnischen Varianten im Analogbereich abzudecken, die ansonsten oftmals Hürden für Automatisierungsansätze darstellen.
A fast transient current-mode buckboost DC-DC converter for portable devices is presented. Running at 1 MHz the converter provides stable 3 V from a 2.7 V to 4.2 V Li-Ion battery. A small voltage under-/overshoot is achieved by fast transient techniques: (1) adaptive pulse skipping (APS) and (2) adaptive compensation capacitance (ACC). The proposed converter was implemented in a 0.25 μm CMOS technology. Load transient simulations confirm the effectiveness of APS and ACC. The improvement in voltage undershoot and response time at light-to-heavy load step (100 mA to 500 mA), are 17 % and 59 %, respectively, in boost mode and 40 % and 49 %, respectively, in buck mode. Similar results are achieved at heavy-to-light load step for overshoot and response time.
Die Spannungsversorgung elektronischer Steuergeräte im Automotive-Bereich wird zunehmend durch Schaltregler sichergestellt. Der SEPIC (Single Ended Primary Inductance Converter) besitzt die Eigenschaft, eine Spannung aufwärts wie auch abwärts wandeln zu können und könnte somit klassische Buck- und Boost-Wandler ablösen. Dieser Beitrag untersucht den SEPIC hinsichtlich Eignung für Automotive-Anwendungen. Dazu wurde eine Groß- sowie Kleinsignalanalyse am Wandler durchgeführt, mit geeigneten Simulationsmodellen nachgebildet und Messungen gegenüber gestellt. Der SEPIC zeigt als Hauptvorteile:
1. einen verzugsfreien Übergang zwischen Buck-/Boost Betrieb, 2. geringe Eingangswelligkeit, 3.DC-Kurzschlussfestigkeit. Auch hinsichtlich Wirkungsgrad und EMV-Verhalten stellt der SEPIC eine interessante Alternative dar. Der zwischen Ein- und Ausgang liegende Kondensator wird dauerhaft von einem Strom durchflossen, auf Basis der Effektivströme wird das damit verbundene Ausfallrisiko diskutiert.
The deterioration of the shielding performance of electromagnetic interference finger stock gaskets in a corrosive environment is investigated. The visualization of the real contact area shows a drastic reduction of the engaged active contact region between fingers and their mating surfaces in presence of corrosives residues. In fact, additional openings occur besides the “Tlike” holes due to the porous nature of gaskets. This leads to a strong degradation of the shielding effectiveness. Modified Bethe’s theory is used to estimate the equivalent circuit parameters while the shielding effectiveness in terms of ratio between two transfer functions is obtained upon applying the filter theory. Quantitative measurements carried out for different gasket types show a good agreement with calculated results, demonstrating thus the validity of the approach.
One of the challenges in condition monitoring systems is the residual life time prediction. This prediction is done based on statistical methods, based on physical knowledge about the considered process or a combination of these approaches. Physical knowledge of the system is a result of long-term experience of process operators. However, it can be gained as well by analyzing appropriately designed process models. The additional benefit of such models is that particular effects and their impact on the process behavior can be analyzed in detail and without plant operation in a shorter time. The current contribution developed in the framework of the research project Model Based Hierarchic Condition Monitoring presents such models for condition monitoring of roller chains. First, already existing high order dynamic models given by nonlinear differential equations of such chains are extended to incorporate effects that occur due to a deterioration of the chain condition. Then, a simple model is developed and compared to the high order model. Based on the two models the change in the process behavior due to a deterioration of the roller chain condition is analyzed to illustrate that these models can be used in future research in the above mentioned research project to better predict the residual life time of the considered roller chains.
This paper presents a laboratory experiment integrating the fields of electronics design, power electronics and drive control. The aim of this experiment is first to illustrate the need for a deep knowledge and the challenges in power electronics and its applications, in this particular case for drive control. The different tasks in this experiment are executed on a complete setup for a brushless dc motor test bench. The tasks assigned to the students are designed such that, in some tasks the knowledge from a particular field, power electronics, electronic design or drive control is deepened, whereas in other tasks the knowledge from more than one of these fields is needed to solve the given problem. Thus, the experiment trains students in the particular domains but illustrates as well the links between power electronics, electronic design and drive control.
Methods for increasing the energy efficiency of induction motors by an appropriate control strategy have been a subject of research during the last years. Several methods for loss minimization have been developed for induction motors operated in a steady state. In recent years, some solutions for the dynamic case have been given as well either using an online or offline optimization approach, implying a certain computational burden, which is undesired in practice. This paper shows that the appropriate application of steady state techniques during transients due to a changing motor torque is a suboptimal strategy with an acceptable performance for efficiency optimization given an induction machine where saturation effects of the main inductance must be considered. The optimization problem is simplified such that a simple suboptimal solution is possible and the quality of the suboptimal solution is investigated by simulations and measurements. The proposed solution is simple, easy to implement, and does not require an online optimization. In addition, the influence of magnetizing induction saturation is considered.
The limited interfaces of today's IC design environments for editing PCell parameters hinder a solid advancement towards more complex analog PCell modules. This paper presents Hierarchical Instance Parameter Editing (HIPE), a highly flexible concept for the customization of PCell sub-instances. Introducing a new type of parameter, HIPE facilitates the dynamic creation of multi-level editing forms reflecting the actual contents of a PCell instance. This approach greatly improves a PCell's ease-of-use, substantially simplifies PCell development, and allows for a hierarchical execution of parameter validation callbacks. Our HIPE implementation has been integrated into a professional PCell development tool and represents a key enabling technology for upcoming generations of high-level hierarchical PCells.