TY - CONF AU - Auroux, Sebastien AU - Karl, Holger ID - 760 T2 - 25th IEEE Annual International Symposium on Personal, Indoor, and Mobile Radio Communication, {PIMRC} 2014, Washington DC, USA, September 2-5, 2014 TI - Flow processing-aware controller placement in wireless DenseNets ER - TY - CONF AU - Schwabe, Arne AU - Karl, Holger ID - 762 T2 - Proceedings of the third workshop on Hot topics in software defined networking, HotSDN '14, Chicago, Illinois, USA, August 22, 2014 TI - Using MAC addresses as efficient routing labels in data centers ER - TY - CONF AU - Blanckenstein, Johannes AU - Karl, Holger ID - 763 T2 - 22nd International Conference on Software, Telecommunications and Computer Networks, SoftCOM 2014, Split, Croatia, September 17-19, 2014 TI - Energy-efficient clock synchronization using wake-up receivers ER - TY - CONF AU - Beister, Frederic AU - Karl, Holger ID - 765 T2 - IEEE 10th International Conference on Wireless and Mobile Computing, Networking and Communications, WiMob 2014, Larnaca, Cyprus, October 8-10, 2014 TI - Predicting mobile video inter-download times with Hidden Markov Models ER - TY - GEN AU - Mehraghdam, Sevil AU - Keller, Matthias AU - Karl, Holger ID - 766 T2 - CoRR TI - Specifying and Placing Chains of Virtual Network Functions ER - TY - GEN AU - Wette, Philip AU - Karl, Holger ID - 767 T2 - CoRR TI - DCT²Gen: A Versatile TCP Traffic Generator for Data Centers ER - TY - GEN AU - Schwabe, Arne AU - Karl, Holger ID - 768 T2 - CoRR TI - Adding Geographical Embedding to AS Topology Generation ER - TY - CHAP AU - Liebendörfer, Michael AU - Ostsieker, Laura ED - Wassong, Thomas ED - Frischemeier, Daniel ED - Fischer, Pascal R. ED - Hochmuth, Reinhard ED - Bender, Peter ID - 8550 SN - 978-3-658-03103-9 978-3-658-03104-6 T2 - Mit Werkzeugen Mathematik und Stochastik lernen – Using Tools for Learning Mathematics and Statistics TI - Mathematik als Werkzeug: Sicht- und Arbeitsweisen von Studierenden am Anfang ihres Mathematikstudiums ER - TY - CONF AU - Liebendörfer, Michael AU - Hochmuth, Reinhard AU - Kolter, Jana AU - Schukajlow, Stanislaw ED - Nicol, C. ED - Oesterle, S. ED - Liljedahl, Peter ED - Allan, D. ID - 8554 T2 - Proceedings of the 38th Conference of the International Group for the Psychology of Mathematics Education an the 36th Conference of the North American Chapter of the Psychology of Mathematics Education TI - The Mathematical Beliefs and Interest Development of Pre-Service Primary Teachers VL - 6 ER - TY - JOUR AU - Liebendörfer, Michael ID - 8557 IS - 4 JF - Oberwolfach Reports TI - Self-determination and interest development of first-year mathematics students VL - 11 ER - TY - CHAP AU - Liebendörfer, Michael AU - Hochmuth, Reinhard AU - Schreiber, Stephan AU - Göller, Robin AU - Kolter, Jana AU - Biehler, Rolf AU - Kortemeyer, Jörg AU - Ostsieker, Laura ED - Roth, Jürgen ED - Ames, J. ID - 8561 T2 - Beiträge zum Mathematikunterricht 2014 TI - Vorstellung eines Fragebogens zur Erfassung von Lernstrategien in mathematikhaltigen Studiengängen ER - TY - JOUR AU - Sergent, S. AU - Kako, S. AU - Bürger, M. AU - Schupp, T. AU - As, Donat Josef AU - Arakawa, Y. ID - 8762 JF - Physical Review B SN - 1098-0121 TI - Polarization properties of single zinc-blende GaN/AlN quantum dots ER - TY - GEN AU - Jovanovikj, Ivan ID - 8842 TI - Detection and Resolution of Data-Flow Differences in Business Process Models ER - TY - CHAP AU - Beutner, Marc AU - Zoyke, A ED - Brucherseifer, M ED - Münk, D ED - Walter, M ID - 9583 T2 - Arbeit der Zukunft – Zukunft der Arbeit TI - Individuelle Bildungsgangarbeit als Antwort auf Fachkräftebedarf und Qualifikationsveränderungen ER - TY - CHAP AU - Beutner, Marc ED - Braukmann, U ED - Dilger, B ED - Kremer, H.-H ID - 9584 T2 - Wirtschaftspädagogische Handlungsfelder. Festschrift für Peter F. E. Sloane zum 60. Geburtstag TI - Bildungsgangarbeit in beruflichen Schulen – Praxisphasen und ihre Auswirkungen in der Bildungsgangarbeit ER - TY - GEN AU - Tönnies, Merle ID - 9627 T2 - Arbeiten aus Anglistik und Amerikanistik TI - Kamm, J. / Lenz, B. (Hg.): Representing Terrorism and Deconstructing Terrorism VL - 39 ER - TY - JOUR AU - Beutner, Marc AU - Fortmann, M AU - Pechuel, R ID - 9656 IS - 58 JF - Kölner Zeitschrift für Wirtschaft und Pädagogik TI - E-Learning zur Sprach- und Berufsförderung – Einblicke in AGnovel. Advanced Graphic novels in der Beruflichen Bildung VL - 29 ER - TY - JOUR AU - Beutner, Marc AU - Fortmann, L. M. ID - 9704 IS - 56 JF - Kölner Zeitschrift für Wirtschaft und Pädagogik TI - Entrepreneurship und Berufliche Bildung: UMW – Under my Wing – Ein Innovationsprojekt zur Unterstützung von Absolventen aus nicht geschäftsbezogenen Disziplinen bei der Unternehmensgründung VL - 29 ER - TY - CHAP AU - Flotmann, Christina ED - Kordts-Freudinger, Robert ED - Urban, Diana ED - Schaper, Nicholas ID - 9722 T2 - Lehr- und Lernpraxis im Fokus – Forschungs- und Reflexionsbeiträge aus der Universität Paderborn TI - Wiki-Wonderland? – Eine Qualitative Analyse zu Vor- und Nachteilen von Wikis für Lehrende und Studierende ER - TY - CHAP AU - Flotmann, Christina ED - Sedlmayr, Gerold ED - Waller, Nicole ID - 9723 T2 - Politics in Fantasy Media: Essays on Ideology and Gender in Fiction, Film, Television and Games TI - Political Rhetoric as a Structural and Ideological Instrument in Star Wars and Harry Potter ER - TY - CHAP AU - Klar, Tilman-Mathies AU - Engbring, Dieter ED - Forbrig, P. ED - Magenheim, J. ID - 9817 T2 - Gestalten und Meistern von Übergängen. 6. Tagung Hochschuldidatik der Informatik TI - Medienbildung mit Informatik-Anteilen!? ER - TY - CONF AB - In order to increase mechanical strength, heat dissipation and ampacity and to decrease failure through fatigue fracture, wedge copper wire bonding is being introduced as a standard interconnection method for mass production. To achieve the same process stability when using copper wire instead of aluminum wire a profound understanding of the bonding process is needed. Due to the higher hardness of copper compared to aluminum wire it is more difficult to approach the surfaces of wire and substrate to a level where van der Waals forces are able to arise between atoms. Also, enough friction energy referred to the total contact area has to be generated to activate the surfaces. Therefore, a friction model is used to simulate the joining process. This model calculates the resulting energy of partial areas in the contact surface and provides information about the adhesion process of each area. The focus here is on the arising of micro joints in the contact area depending on the location in the contact and time. To validate the model, different touchdown forces are used to vary the initial contact areas of wire and substrate. Additionally, a piezoelectric tri-axial force sensor is built up to identify the known phases of pre-deforming, cleaning, adhering and diffusing for the real bonding process to map with the model. Test substrates as DBC and copper plate are used to show the different formations of a wedge bond connection due to hardness and reaction propensity. The experiments were done by using 500 $\mu$m copper wire and a standard V-groove tool. AU - Althoff, Simon AU - Neuhaus, Jan AU - Hemsel, Tobias AU - Sextro, Walter ID - 9868 KW - adhesion KW - circuit reliability KW - deformation KW - diffusion KW - fatigue cracks KW - friction KW - interconnections KW - lead bonding KW - van der Waals forces KW - Cu KW - adhering process KW - adhesion process KW - ampacity improvement KW - bond quality improvement KW - cleaning process KW - diffusing process KW - fatigue fracture failure KW - friction energy KW - friction model KW - heat dissipation KW - mechanical strength KW - piezoelectric triaxial force sensor KW - predeforming process KW - size 500 mum KW - total contact area KW - van der Waals forces KW - wedge copper wire bonding KW - Bonding KW - Copper KW - Finite element analysis KW - Force KW - Friction KW - Substrates KW - Wires T2 - Electronic Components and Technology Conference (ECTC), 2014 IEEE 64th TI - Improving the bond quality of copper wire bonds using a friction model approach ER - TY - CONF AB - Cavitation monitoring is desired to optimize the sonication for diverse sonochemical processes and to detect changes or malfunctions during operation. In situ cavitation measurements can be carried out by detection of the acoustic emissions of cavitation bubbles by sensors in the liquid. However, in harsh environments sensors might not be applicable. Thus, the impact of cavitation on the electrical signals of a piezoelectric transducer has been analyzed as alternative method to measure the threshold, strength and type of cavitation. The applicability has been tested in three different setups to evaluate the general- izability of extracted indicators. In all setups indicators for the cavitation thresholds could be derived from the current signal. In two setups features showed two thresholds that may be linked to the types of cavitation. However, only one feature derived from the current signal in one particular setup correlated to the strength of cavitation. Cavitation detection based on the current signal of the transducer is a useful method to detect cavitation in harsh environments and without perturbing the sound field. Once appli- cable indicators have been identified, they may easily be tracked during the process. However, for more detailed studies about the cavitation activity and its spatial distribution, measurements with in situ sensors are recommended. AU - Bornmann, Peter AU - Hemsel, Tobias AU - Sextro, Walter AU - Memoli, Gianluca AU - Hodnett, Mark AU - Zeqiri, Bajram ID - 9869 SN - 9781479970490 T2 - 2014 IEEE International Ultrasonics Symposium Proceedings TI - Self-Sensing Ultrasound Transducer for Cavitation Detection ER - TY - CONF AB - Nowadays wire bonding is a widely-used technology for interconnecting chips in the packaging industry. Thereby, it is known that the bond quality massively depends upon the microstructure prevailing in the bond and consequently the materials used as well as the bonding parameters. However the actually used materials such as aluminum and gold are either characterized by comparibly poor conductivity or high costs, respectively. Due to its outstanding properties copper is a more attractive candidate. Still, a thorough investigation on the interrelationship between the material combinations, the processing parameters and the resulting microstructure for copper and aluminum wire bonding was not carried out yet. Depending on the aforementioned factors the microstructural evolution can be completely different during the bonding process. Therefore, this study focuses on the microstructural evolution of heavy copper and heavy aluminum wires bonded on copper substrates. The evolution of the wire microstructure as well as the wire-substrate-interface was investigated by scanning electron microscope in combination with electron backscatter diffraction and microhardness measurements. Various samples were extracted at different points of the bonding process, namely the as-received condition, after touchdown and after completed bonding. The results of the aluminum and copper wires were compared to each other in both longitudinal and transversal direction. It was found, that the two wire materials were completely different in the as-received condition regarding the grain size, the grain morphology, the texture and the microhardness. After touchdown the microstructure did not show significant changes in both materials, yet a strain-hardening was observed in the copper wire resulting from the touchdown force. When the bonding process was completed a different microstructure could be observed in both the wire as well as the layer for the materials investigated. Furthermore, a destinctive increase in the wire hardness could be found in case of copper, which was not observed for the aluminum wire. The ramifications between the two wire materials presented in this work will be discussed with the objective of optimizing the quality of the bonds. AU - Eacock , Florian AU - Schaper, Mirko AU - Althoff, Simon AU - Unger, Andreas AU - Eichwald, Paul AU - Hengsbach, Florian AU - Zinn, Carolin AU - Holzweissig, Martin Joachim AU - Guth, Karsten ID - 9870 KW - Bonding KW - Copper KW - Microstructure evolution T2 - Proceedings of the 47th International Symposium on Microelectronics TI - Microstructural investigations of aluminum and copper wire bonds ER - TY - CONF AB - Wire bonding is the most common technology for connecting electronic components. Due to their efficiency bond interconnections made of copper wire are used for example in the aerospace and medical technology as well as in the fields of renewable energies. One of the main cost factors in the manufacturing process is the consumables like bonding tools. The technological transition to copper as wire material causes significant wear on the millimeter large effective contact area of the bonding tool. This wear leads to a loss by a factor of 30 of the number of reliable interconnections which can be produced by a single tool. To reduce setting-up time in the production and minimizing costs, an enlarged bonding tool lifetime is desirable. Consequently a better understanding of wear and recognition of wear pattern is required. Therefore, the paper presents an analyzing method of the tool topography change of a heavy wire bonding tool by using a confocal microscope. Furthermore, the paper discusses the identification of the main wear indicators by the help of the named topography change for different bond parameters, like ultrasonic power and tool geometry. Reference topography has been carried out by choosing typical parameters of the production line. To judge whether the quality requirement of the bond connections made by a single tool cannot be fulfilled shear test of the source bond have been carried out after a defined number of produced bond connections. Main steps of analysis: (I)Topography of the tool surface is sampled after a defined number of bonds by means of a confocal microscope to detect the wear progress.(II)The recorded data is filtered using Matlab. So, measurement errors can be eliminated and the topography can be overlaid more easy to identify differences between diverse tools or differences in wear stages of the same tool.(III)The subsequent discretization of the topography into sub volumes allows to (IV)describe the loss of volume depending on the position in the groove. Thereby, intermediate status of wear of one tool can be used to obtain a persistent description of the topography change over the number of produced bonds by interpolating the confocal data. Afterwards the persistent change of the groove flank has been analyzed for the named test series to identify the main wear indicators and their effect on shear forces. All worn tools show dominant areas for volume loss especially for plastic deformation and accordingly abrasion. These wear mechanism can be referred to the change of main parts of the groove geometry like the rounding of the front and back radius. The most volume loss was identified in the upper part of the tool flanks or rather at the transition from the groove flank to the front or back radius. Furthermore the observation of the center of the groove flank shows just a little change in volume. All in all, the identification of the wear indicators will be discussed with the objective of increasing the tool lifetime by optimizing the tool geometry without losses in bond quality and reliability. AU - Eichwald, Paul AU - Sextro, Walter AU - Althof, Simon AU - Eacock, Florian AU - Unger, Andreas AU - Meyer, Tobias AU - Guth, Karsten ID - 9871 KW - wedge/wedge bonding KW - copper wire KW - tool wear T2 - Proceedings of the 47th International Symposium on Microelectronics TI - Analysis Method of Tool Topography Change and Identification of Wear Indicators for Heavy Copper Wire Wedge Bonding ER - TY - BOOK AB - Intelligent technical systems, which combine mechanical, electrical and software engineering with methods from control engineering and advanced mathematics, go far beyond the state of the art in mechatronics and open up fascinating perspectives. Among these systems are so-called self-optimizing systems, which are able to adapt their behavior autonomously and flexibly to changing operating conditions. The Collaborative Research Center 614 "Self-optimizing concepts and structures in mechanical engineering" pursued the long-term aim to enable others to develop dependable self-optimizing systems. Assuring their dependability poses new challenges. However, self-optimization also offers the possibility to adapt the system's behavior to improve dependability during operation. The aim of this book is to provide methods and techniques to master the challenges and to exploit the possibilities given by self-optimization. The reader will be able to develop self-optimizing systems that fulfill and surpass today’s dependability requirements easily. This book is directed to researchers and practitioners alike. It gives a brief introduction to the holistic development approach for self-optimizing mechatronic systems and the steps required to assure a dependable product design starting with the very early conceptual design phase. A guideline to select suitable methods for each step and the methods themselves are included. Each method is individually introduced, many examples and full references are given. AU - Gausemeier, Jürgen AU - Josef Rammig, Franz AU - Schäfer, Wilhelm AU - Sextro, Walter ID - 9873 TI - Dependability of Self-Optimizing Mechatronic Systems VL - Lecture Notes in Mechanical Engineering ER - TY - JOUR AU - Hemsel, Tobias AU - Bornmann, Peter AU - Morita, Takeshi AU - Sondermann-Wölke, Christoph AU - Sextro, Walter ID - 9874 JF - Archive of Applied Mechanics KW - Reliability KW - Ultrasonic power transducers KW - FMEA SN - 0939-1533 TI - Reliability analysis of ultrasonic power transducers ER - TY - JOUR AB - Piezoelectric inertia motors use the inertia of a body to drive it by means of a friction contact in a series of small steps. It has been shown previously in theoretical investigations that higher velocities and smoother movements can be obtained if these steps do not contain phases of stiction (''stick-slip`` operation), but use sliding friction only (''slip-slip`` operation). One very promising driving option for such motors is the superposition of multiple sinusoidal signals or harmonics. In this contribution, the theoretical results are validated experimentally. In this context, a quick and reliable identification process for parameters describing the friction contact is proposed. Additionally, the force generation potential of inertia motors is investigated theoretically and experimentally. The experimental results confirm the theoretical result that for a given maximum frequency, a signal with a high fundamental frequency and consisting of two superposed sine waves leads to the highest velocity and the smoothest motion, while the maximum motor force is obtained with signals containing more harmonics. These results are of fundamental importance for the further development of high-velocity piezoelectric inertia motors. AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9876 JF - Archive of Applied Mechanics KW - Inertia motor KW - High velocity KW - Stick-slip motor KW - Slip-slip operation KW - Friction parameter identification SN - 0939-1533 TI - High-velocity operation of piezoelectric inertia motors: experimental validation ER - TY - JOUR AB - (K,Na)NbO3 ceramics have attracted much attention as lead-free piezoelectric materials with high piezoelectric properties. High-quality (K,Na)NbO3 ceramics can be sintered using KNbO3 and NaNbO3 powders synthesized by a hydrothermal method. In this study, to enhance the quality factor of the ceramics, high-power ultrasonic irradiation was employed during the hydrothermal method, which led to a reduction in the particle size of the resultant powders. AU - Isobe, G. AU - Maeda, Takafumi AU - Bornmann, Peter AU - Hemsel, Tobias AU - Morita, Takeshi ID - 9878 IS - 2 JF - Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on KW - Q-factor KW - ceramics KW - crystal growth from solution KW - particle size KW - piezoelectric materials KW - potassium compounds KW - powders KW - sintering KW - sodium compounds KW - ultrasonic effects KW - (K0.48Na0.52)NbO3 KW - KNbO3 powders KW - NaNbO3 powders KW - high-power ultrasonic irradiation KW - lead-free piezoelectric materials KW - lead-free piezoelectric powders KW - particle size reduction KW - piezoelectric properties KW - quality factor KW - sintered (K0.48Na0.52)NbO3 ceramics KW - sintering KW - ultrasonic-assisted hydrothermal method KW - Acoustics KW - Ceramics KW - Lead KW - Piezoelectric materials KW - Powders KW - Radiation effects KW - Transducers SN - 0885-3010 TI - Synthesis of lead-free piezoelectric powders by ultrasonic-assisted hydrothermal method and properties of sintered (K0.48Na0.52)NBO3 ceramics VL - 61 ER - TY - CONF AB - Application of prognostics and health management (PHM) in the field of Proton Exchange Membrane (PEM) fuel cells is emerging as an important tool in increasing the reliability and availability of these systems. Though a lot of work is currently being conducted to develop PHM systems for fuel cells, various challenges have been encountered including the self-healing effect after characterization as well as accelerated degradation due to dynamic loading, all which make RUL predictions a difficult task. In this study, a prognostic approach based on adaptive particle filter algorithm is proposed. The novelty of the proposed method lies in the introduction of a self-healing factor after each characterization and the adaption of the degradation model parameters to fit to the changing degradation trend. An ensemble of five different state models based on weighted mean is then developed. The results show that the method is effective in estimating the remaining useful life of PEM fuel cells, with majority of the predictions falling within 5\% error. The method was employed in the IEEE 2014 PHM Data Challenge and led to our team emerging the winner of the RUL category of the challenge. AU - Kimotho, James Kuria AU - Meyer, Tobias AU - Sextro, Walter ID - 9879 KW - ageing KW - particle filtering (numerical methods) KW - proton exchange membrane fuel cells KW - remaining life assessment KW - PEM fuel cell prognostics KW - PHM KW - RUL predictions KW - accelerated degradation KW - adaptive particle filter algorithm KW - dynamic loading KW - model parameter adaptation KW - prognostics and health management KW - proton exchange membrane fuel cells KW - remaining useful life estimation KW - self-healing effect KW - Adaptation models KW - Data models KW - Degradation KW - Estimation KW - Fuel cells KW - Mathematical model KW - Prognostics and health management T2 - Prognostics and Health Management (PHM), 2014 IEEE Conference on TI - PEM fuel cell prognostics using particle filter with model parameter adaptation ER - TY - CONF AB - With the paradigm shift towards prognostic and health management (PHM) of machinery, there is need for reliable PHM methodologies with narrow error bounds to allow maintenance engineers take decisive maintenance actions based on the prognostic results. Prognostics is mainly concerned with the estimation of the remaining useful life (RUL) or time to failure (TTF). The accuracy of PHM methods is usually a function of the features extracted from the raw data obtained from sensors. In cases where the extracted features do not display clear degradation trends, for instance highly loaded bearings, the accuracy of the state of the art PHM methods is significantly affected. The data which lacks clear degradation trend is referred to as non-trending data. This study presents a method for extracting degradation trends from non-trending condition monitoring data for RUL estimation. The raw signals are first filtered using a discrete wavelet transform (DWT) denoising filter to remove noise from the acquired signals. Time domain, frequency domain and time-frequency domain features are then extracted from the filtered signals. An autoregressive model is then applied to the extracted features to identify the degradation trends. Features representing the maximum health information are then selected based on a performance evaluation criteria using extreme learning machine (ELM) algorithm. The selected features can then be used as inputs in a prognostic algorithm. The feasibility of the method is demonstrated using experimental bearing vibration data. The performance of the method is evaluated on the accuracy of RUL estimation and the results show that the method can be used to accurately estimate RUL with a maximum error of 10\%. AU - Kimotho, James Kuria AU - Sextro, Walter ID - 9880 KW - autoregressive model ELM feature extraction feature selection non-trending Remaining useful Life T2 - Proceedings of the Second European Conference of the Prognostics and Health Management Society 2014 TI - An approach for feature extraction and selection from non-trending data for machinery prognosis VL - 5 ER - TY - JOUR AB - The increasing demand for high reliability, safety and availability of technical systems calls for innovative maintenance strategies. The use of prognostic health management (PHM) approach where maintenance action is taken based on current and future health state of a component or system is rapidly gaining popularity in the maintenance industry. Multiclass support vector machines (MC-SVM) has been identified as a promising algorithm in PHM applications due to its high classification accuracy. However, it requires parameter tuning for each application, with the objective of minimizing the classification error. This is a single objective optimization problem which requires the use of optimization algorithms that are capable of exhaustively searching for the global optimum parameters. This work proposes the use of hybrid differential evolution (DE) and particle swarm optimization (PSO) in optimally tuning the MC-SVM parameters. DE identifies the search limit of the parameters while PSO finds the global optimum within the search limit. The feasibility of the approach is verified using bearing run-to-failure data and the results show that the proposed method significantly increases health state classification accuracy. AU - Kimotho, James Kuria AU - Sextro, Walter ID - 9881 IS - 1 JF - PAMM SN - 1617-7061 TI - Optimal Parameter Tuning for Multiclass Support Vector Machines in Machinery Health State Estimation VL - 14 ER - TY - JOUR AB - An automotive suspension system represents one of the most complex and important systems in a passenger vehicle, which has to ensure a robust and optimized contact between the wheels and the road at any time. For improving a suspension system it is important to take an investigative look at the interaction between suspension, tire and road dynamics. Thus a part of a study into aspects of suspension modeling on multi-body simulations of rear multi-link suspension system dynamics with focus on the tire footprint area is presented in this work. AU - Kohl, Sergej AU - Sextro, Walter AU - Zuber, Armin ID - 9882 IS - 1 JF - PAMM SN - 1617-7061 TI - Tire footprint analysis depending on the elastokinematics of a multi-link suspension system using multi-body dynamics simulation VL - 14 ER - TY - CHAP AU - Meyer, Tobias AU - Priesterjahn, Claudia AU - Sextro, Walter ED - Gausemeier, Jürgen ED - Josef Rammig, Franz ED - Schäfer, Wilhelm ED - Sextro, Walter ID - 9883 SN - 978-3-642-53741-7 T2 - Dependability of Self-Optimizing Mechatronic Systems TI - Conclusion and Outlook ER - TY - CONF AB - So-called reliability adaptive systems are able to adapt their system behavior based on the current reliability of the system. This allows them to react to changed operating conditions or faults within the system that change the degradation behavior. To implement such reliability adaptation, self-optimization can be used. A self-optimizing system pursues objectives, of which the priorities can be changed at runtime, in turn changing the system behavior. When including system reliability as an objective of the system, it becomes possible to change the system based on the current reliability as well. This capability can be used to control the reliability of the system throughout its operation period in order to achieve a pre-defined or user-selectable system lifetime. This way, optimal planning of maintenance intervals is possible while also using the system capabilities to their full extent. Our proposed control system makes it possible to react to changed degradation behavior by selecting objectives of the self-optimizing system and in turn changing the operating parameters in a closed loop. A two-stage controller is designed which is used to select the currently required priorities of the objectives in order to fulfill the desired usable lifetime. Investigations using a model of an automotive clutch system serve to demonstrate the feasibility of our controller. It is shown that the desired lifetime can be achieved reliably. AU - Meyer , Tobias AU - Sextro, Walter ID - 9884 KW - self-optimization reliability adaptive T2 - Proceedings of the Second European Conference of the Prognostics and Health Management Society 2014 TI - Closed-loop Control System for the Reliability of Intelligent Mechatronic Systems VL - 5 ER - TY - JOUR AB - Intelligent mechatronic systems, such as self-optimizing systems, allow an adaptation of the system behavior at runtime based on the current situation. To do so, they generally select among several pre-defined working points. A common method to determine working points for a mechatronic system is to use model-based multiobjective optimization. It allows finding compromises among conflicting objectives, called objective functions, by adapting parameters. To evaluate the system behavior for different parameter sets, a model of the system behavior is included in the objective functions and is evaluated during each function call. Intelligent mechatronic systems also have the ability to adapt their behavior based on their current reliability, thus increasing their availability, or on changed safety requirements; all of which are summed up by the common term dependability. To allow this adaptation, dependability can be considered in multiobjective optimization by including dependability-related objective functions. However, whereas performance-related objective functions are easily found, formulation of dependability-related objective functions is highly system-specific and not intuitive, making it complex and error-prone. Since each mechatronic system is different, individual failure modes have to be taken into account, which need to be found using common methods such as Failure-Modes and Effects Analysis or Fault Tree Analysis. Using component degradation models, which again are specific to the system at hand, the main loading factors can be determined. By including these in the model of the system behavior, the relation between working point and dependability can be formulated as an objective function. In our work, this approach is presented in more detail. It is exemplified using an actively actuated single plate dry clutch system. Results show that this approach is suitable for formulating dependability-related objective functions and that these can be used to extend system lifetime by adapting system behavior. AU - Meyer , Tobias AU - Sondermann-Wölke, Christoph AU - Sextro, Walter ID - 9885 JF - Conference Proceedings of the 2nd International Conference on System-Integrated Intelligence KW - Self-optimization KW - multiobjective optimization KW - objective function KW - dependability KW - intelligent system KW - behavior adaptation TI - Method to Identify Dependability Objectives in Multiobjective Optimization Problem VL - 15 ER - TY - CONF AB - A model to calculate the locally resolved tangential contact forces of the wheel rail contact with respect to contact kinematics, material and surface properties as well as temperature is introduced. The elasticity of wheel and rail is modeled as an elastic layer consisting of point contact elements connected by springs to each other and to the wheel. Each element has two degrees of freedom in tangential directions. The resulting total stiffness matrix is reduced to calculate only the position of the elements in contact. Friction forces as well as contact stiffnesses are incorporated by a nonlinear force-displacement characteristic, which originates from a detailed contact model. The contact elements are transported through the contact zone in discrete time steps. After each time step an equilibrium is calculated. For all elements, their temperature and its influence on local friction are regarded by calculating friction power and temperature each time step. AU - Neuhaus, Jan AU - Sextro, Walter ED - Liu, G.R. ED - Guan, Z.W. ID - 9887 KW - Rolling Contact KW - Discrete Elements KW - Contact Stiffness KW - Temperature T2 - Proceedings of the 5th International Conference on Computational Methods TI - Thermo-Mechanical Model for Wheel Rail Contact using Coupled Point Contact Elements ER - TY - JOUR AB - This paper discusses the refinement of multibody models by integration of flexible bodies and by considering nonlinearities from contacts. It presents common approaches for contact modeling in multibody simulations and strategies to include flexible bodies. A contact model is implemented in the elastic multibody model. Experimental results show that significant effects of system dynamics can be modeled by use of a multibody model including elastic bodies and contacts. AU - Schulze, Sebastian AU - Sextro, Walter AU - Grüter, Frank ID - 9888 IS - 1 JF - PAMM SN - 1617-7061 TI - Contact Modeling in Multibody Systems with Elastic Bodies in High-Frequency Applications VL - 14 ER - TY - CONF AB - A measurement method is presented that combines the advantages of the multisine measurement technique with a prediction method for peak bending behavior. This combination allows the analysis of the dynamic behavior of mechanical structures at distinctly reduced measurement durations and has the advantage of reducing high excitation impacts on the structure under test. AU - Sprock, Christian AU - Sextro, Walter ID - 9889 KW - bending KW - dynamic testing KW - measurement KW - structural engineering KW - vibrations KW - measurement durations KW - mechanical structures KW - multisine measurement technique KW - nonlinear peak bending behavior KW - prediction method KW - time-efficient dynamic analysis KW - Heuristic algorithms KW - Nonlinear systems KW - Oscillators KW - Time measurement KW - Time-frequency analysis KW - Vibrations T2 - Instrumentation and Measurement Technology Conference (I2MTC) Proceedings, 2014 IEEE International TI - Time-efficient dynamic analysis of structures exhibiting nonlinear peak bending ER - TY - CONF AB - Many nonlinear mechanical oscillators show excitation-dependent behavior. In this paper, a new measurement approach is presented to analyze such structures. The main advantage of the presented method is the high efficiency, since measurement duration and loads to the structure are significantly reduced. AU - Sprock, Christian AU - Sextro, Walter ID - 9890 T2 - Proceedings in Applied Mathematics and Mechanics 14 (2014), Nr. 1, TI - Time-efficient analysis of nonlinear dynamic behavior. ER - TY - CONF AB - A measurement method is presented that combines the advantages of the multisine measurement technique with a prediction method for peak bending behavior. This combination allows the analysis of the dynamic behavior of mechanical structures at distinctly reduced measurement durations and has the advantage of reducing high excitation impacts on the structure under test. After a brief presentation of the algorithm, the validity scope of the approach is investigated with emphasis on an exemplary error investigation. AU - Sprock, Christian AU - Sextro, Walter ID - 9891 T2 - Proceedings of ISMA - International Conference of Noise and Vibration. 2014 TI - Time-efficient analysis of nonlinear peak bending behavior. ER - TY - CONF AU - Sprock, Christian AU - Sextro, Walter ID - 9892 T2 - Proceedings of 31st Danubia-Adria Symposium. 2014 TI - Vibration Analysis of Mechanical Structures using Multisine Excitation Techniques ER - TY - CHAP AU - Trächtler, Ansgar AU - Hölscher, Christian AU - Rasche, Christoph AU - Priesterjahn, Claudia AU - Zimmer, Detmar AU - Henning Keßler, Jan AU - Stahl, Katharin AU - Flaßkamp, Kathrin AU - Vaßholz, Mareen AU - Krüger, Martin AU - Dellnitz, Michael AU - Iwanek, Peter AU - Reinold, Peter AU - Hartmann, Philip AU - Meyer, Tobias AU - Sextro, Walter ED - Gausemeier, Jürgen ED - Josef Rammig, Franz ED - Schäfer, Wilhelm ED - Sextro, Walter ID - 9893 SN - 978-3-642-53741-7 T2 - Dependability of Self-Optimizing Mechatronic Systems TI - Introduction to Self-optimization and Dependability ER - TY - CHAP AU - Trächtler, Ansgar AU - Kleinjohann, Bernd AU - Heinzemann, Christian AU - Rasche, Christoph AU - Priesterjahn, Claudia AU - Steenken, Dominik AU - Wehrheim, Heike AU - Gausemeier, Jürgen AU - Flaßkamp, Kathrin AU - Kleinjohann, Lisa AU - Krüger, Martin AU - Iwanek, Peter AU - Hartmann, Philip AU - Dorociak, Rafal AU - Groesbrink, Stefan AU - Ziegert, Steffen AU - Meyer, Tobias AU - Sextro, Walter AU - Schäfer, Wilhelm ED - Gausemeier, Jürgen ED - Josef Rammig, Franz ED - Schäfer, Wilhelm ED - Sextro, Walter ID - 9894 SN - 978-3-642-53741-7 T2 - Dependability of Self-Optimizing Mechatronic Systems TI - Case Study ER - TY - CONF AB - Power semiconductor modules are used to control and switch high electrical currents and voltages. Within the power module package wire bonding is used as an interconnection technology. In recent years, aluminum wire has been used preferably, but an ever-growing market of powerful and efficient power modules requires a material with better mechanical and electrical properties. For this reason, a technology change from aluminum to copper is indispensable. However, the copper wire bonding process reacts more sensitive to parameter changes. This makes manufacturing reliable copper bond connections a challenging task. The aim of the BMBF funded project Itsowl-InCuB is the development of self-optimizing techniques to enable the reliable production of copper bond connections under varying conditions. A model of the process is essential to achieve this aim. This model needs to include the dynamic elasto-plastic deformation, the ultrasonic softening effect and the proceeding adhesion between wire and substrate. This paper focusses on the pre-deformation process. In the touchdown phase, the wire is pressed into the V-groove of the tool and a small initial contact area between wire and substrate arise. The local characteristics of the material change abruptly because of the cold forming. Consequently, the pre-deformation has a strong effect on the joining process. In [1], a pre-cleaning effect during the touchdown process of aluminum wires by cracking of oxide layers was presented. These interactions of the process parameters are still largely unknown for copper. In a first step, this paper validates the importance of modeling the pre-deformation by showing its impact on the wire deformation characteristic experimentally. Creating cross-section views of pre-deformed copper wires has shown a low deformation degree compared to aluminum. By using a digital microscope and a scanning confocal microscope an analysis about the contact areas and penetration depths after touchdown has been made. Additionally, it has to be taken into account that the dynamical touchdown force depends on the touchdown speed and the touchdown force set in the bonding machine. In order to measure the overshoot in the force signals, a strain gauge sensor has been used. Subsequently, the affecting factors have been interpreted independently Furthermore, the material properties of copper wire have been investigated with tensile tests and hardness measurements. In a second step, the paper presents finite element models of the touchdown process for source and destination bonds. These models take the measured overshoot in the touchdown forces into account. A multi-linear, isotropic material model has been selected to map the material properties of the copper. A validation of the model with the experimental determined contact areas, normal pressures and penetration depths reveals the high model quality. Thus, the simulation is able to calculate and visualize the three dimensional pre-deformation with an integrated material parameter of the wire if the touchdown parameters of the bonding machine are known. Based on the calculated deformation degrees of wire and substrate, it is probably possible to investigate the effect of the pre-deformation on the pre-cleaning phase in the copper wire bonding. AU - Unger, Andreas AU - Sextro, Walter AU - Althoff, Simon AU - Eichwald, Paul AU - Meyer, Tobias AU - Eacock, Florian AU - Brökelmann, Michael ID - 9895 KW - pre-deformation KW - copper wire bonding KW - finite element model T2 - Proceedings of the 47th International Symposium on Microelectronics (IMAPS) TI - Experimental and Numerical Simulation Study of Pre-Deformed Heavy Copper Wire Wedge Bonds ER - TY - CONF AB - In power electronics, ultrasonic wire bonding is used to connect the electrical terminals of power modules. To implement a self-optimization technique for ultrasonic wire bonding machines, a model of the process is essential. This model needs to include the so called ultrasonic softening effect. It is a key effect within the wire bonding process primarily enabling the robust interconnection between the wire and a substrate. However, the physical modeling of the ultrasonic softening effect is notoriously difficult because of its highly non-linear character and the absence of a proper measurement method. In a first step, this paper validates the importance of modeling the ultrasonic softening by showing its impact on the wire deformation characteristic experimentally. In a second step, the paper presents a data-driven model of the ultrasonic softening effect which is constructed from data using machine learning techniques. A typical caveat of data-driven modeling is the need for training data that cover the considered domain of process parameters in order to achieve accurate generalization of the trained model to new process configurations. In practice, however, the space of process parameters can only be sampled sparsely. In this paper, a novel technique is applied which enables the integration of prior knowledge about the process into the datadriven modeling process. It turns out that this approach results in accurate generalization of the data-driven model to unseen process parameters from sparse data. AU - Unger, Andreas AU - Sextro, Walter AU - Althoff, Simon AU - Meyer, Tobias AU - Brökelmann, Michael AU - Neumann, Klaus AU - Reimann, René Felix AU - Guth, Karsten AU - Bolowski, Daniel ID - 9896 T2 - Proceedings of 8th International Conference on Integrated Power Electronic Systems TI - Data-driven Modeling of the Ultrasonic Softening Effect for Robust Copper Wire Bonding VL - 141 ER - TY - GEN AU - Brummel, NinaMadeleine ID - 392 TI - On the Relation between Innovation and Competion: The Case of Energy Industry ER - TY - CONF AB - A fundamental problem for peer-to-peer systems is to maintain connectivity while nodes are leaving, i.e., the nodes requesting to leave the peer-to-peer system are excluded from the overlay network without affecting its connectivity. There are a number of studies for safe node exclusion if the overlay is in a well-defined state initially. Surprisingly, the problem is not formally studied yet for the case in which the overlay network is in an arbitrary initial state, i.e., when looking for a self-stabilizing solution for excluding leaving nodes. We study this problem in two variants: the Finite Departure Problem (FDP) ) and the Finite Sleep Problem (FSP). In the FDP the leaving nodes have to irrevocably decide when it is safe to leave the network, whereas in the FSP, this leaving decision does not have to be final: the nodes may resume computation if necessary. We show that there is no self-stabilizing distributed algorithm for the FDP, even in a synchronous message passing model. To allow a solution, we introduce an oracle called NIDEC and show that it is sufficient even for the asynchronous message passing model by proposing an algorithm that can solve the FDP using NIDEC. We also show that a solution to the FSP does not require an oracle. AU - Foreback, Dianne AU - Koutsopoulos, Andreas AU - Nesterenko, Mikhail AU - Scheideler, Christian AU - Strothmann, Thim Frederik ID - 393 T2 - Proceedings of the 16th International Symposium on Stabilization, Safety, and Security of Distributed Systems TI - On Stabilizing Departures in Overlay Networks ER - TY - JOUR AB - The relevance of our definition for sensitivity in refractometric sensing, being the relative change in the transmittance of a certain output channel of an optical device over the change in the refractive index of the probed material, is discussed. It is compared to one based on spectral shift per refractive index unit change. Further, there is discussion on how group delay and sensitivity are interrelated and can be converted into each other and which physical quantities are relevant for high sensitivity. As a by-product of the theory presented, a general expression relating group delay and the ratio of the time-averaged optical energy and the input power is presented. AU - Hoekstra, Hugo J. W. M. AU - Hammer, Manfred ID - 3937 IS - 7 JF - Journal of the Optical Society of America B KW - tet_topic_waveguide SN - 0740-3224 TI - General relation for group delay and the relevance of group delay for refractometric sensing VL - 31 ER - TY - CONF AB - Service Oriented Architectures (SOAs) enable the reuse and substitution of software services to develop highly flexible software systems. To benefit from the growing plethora of available services, sophisticated service discovery approaches are needed that bring service requests and offers together. Such approaches rely on rich service descriptions, which specify also the behavior of provided/requested services, e.g., by pre- and postconditions of operations. As a base for the specification a data schema is used, which specifies the used data types and their relations. However, data schemas are typically heterogeneous wrt. their structure and terminology, since they are created individually in their diverse application contexts. As a consequence the behavioral models that are typed over the heterogeneous data schemas, cannot be compared directly. In this paper, we present an holistic approach to normalize rich service description models to enable behavior-aware service discovery. The approach consists of a matching algorithm that helps to resolve structural and terminological heterogeneity in data schemas by exploiting domain-specific background ontologies. The resulting data schema mappings are represented in terms of Query View Transformation (QVT) relations that even reflect complex n:m correspondences. By executing the transformation, behavioral models are automatically normalized, which is a prerequisite for a behavior-aware operation matching. AU - Schwichtenberg, Simon AU - Gerth, Christian AU - Huma, Zille AU - Engels, Gregor ID - 394 T2 - Proceedings of the 10th European Conference on Modelling Foundations and Applications (ECMFA) TI - Normalizing Heterogeneous Service Description Models with Generated QVT Transformations ER -