On the discretization of a bistable cantilever beam with application to energy harvesting

A typical setup for energy harvesting is that of a cantilever beam with piezoceramics excited by ambient base vibrations. In order to get higher energy output for a wide range of excitation frequencies, often a nonlinearity is introduced by intention in that way, that two magnets are fixed close to the free tip of the beam. Depending on strength and position of the magnets, this can either result in a mono-, bi- or tristable system. In our study, we focus on a bistable system. Such systems have been investigated thoroughly in literature while in almost all cases the beam has been discretized by a single shape function, in general the first eigenshape of the linear beam with undeflected stable equilibrium position. There can be some doubts about the suitability of a discretization by a single shape function mainly due to two reasons. First: In case of stochastic broadband excitations a discretization, taking into consideration just the first vibration shape seems not to be reasonable. Second: as the undeflected position of the considered system is unstable and the system significantly nonlinear, the question arises, if using just one eigenshape of the linear beam is a suitable approximation of the operation shapes during excited oscillations even in the case of harmonic excitation. Are there other, e.g. amplitude dependent, possibilities and/or should multiple ansatz functions be considered instead? In this paper, we focus mainly on the second point. Therefore, a bistable cantilever beam with harmonic base excitation is considered and experimental investigations of operation shapes are performed using a high-speed camera. The observed operation shapes are expanded in a similar way as it is done in a theoretical analysis by a corresponding mixed Ritz ansatz. The results show the existence of distinct superharmonics (as one can expect for a nonlinear system) but additionally the necessity to use more than one shape function in the discretization, covering also the amplitude dependence of the observed operation shapes

Visual Computing als Basis für Prozessinnovation im Produktlebenszyklus

Aus der Einführung: "Die Informationstechnik ist seit den Anfängen von CAD vor ca. 50 Jahren ein wesentlicher Impulsgeber für die Produktentwicklung und hat maßgeblichen Anteil an Prozessinnovationen wie dem Global Engineering oder der Digitalen Fabrik. Längst geht es aber heute nicht mehr allein um die Geometriebeschreibung zukünftiger Produkte, sondern um die möglichst umfassende Begleitung und Ergänzung des realen Produkts durch das virtuelle Produkt: von der ersten Idee bis zum Recycling. Die umfassende Vision des virtuellen Produkts als Pendant zum realen Produkt (Spur & Krause 1997) ist untrennbar mit dem Fortschritt der Informationstechnologie verbunden.

Iterative Next Boundary Detection for Instance Segmentation of Tree Rings in Microscopy Images of Shrub Cross Sections

We address the problem of detecting tree rings in microscopy images of shrub cross sections. This can be regarded as a special case of the instance segmentation task with several unique challenges such as the concentric circular ring shape of the objects and high precision requirements that result in inadequate performance of existing methods. We propose a new iterative method which we term Iterative Next Boundary Detection (INBD). It intuitively models the natural growth direction, starting from the center of the shrub cross section and detecting the next ring boundary in each iteration step. In our experiments, INBD shows superior performance to generic instance segmentation methods and is the only one with a built-in notion of chronological order. Our dataset and source code are available at http://github.com/alexander-g/INBD.Comment: CVPR 202

Integration des Community-Gedankens in das Collaborative Engineering am Beispiel des Schiffbaus

E-Collaboration als aktuell vieldiskutierte Form der zwischenbetrieblichen Zusammenarbeit bietet Unternehmen auch im Bereich der Produktentwicklung neue Möglichkeiten, dem steigenden Wettbewerbsdruck zu begegnen. Zielsetzung dieses Beitrages ist es, das Konzept des Collaborative Engineering darzustellen und durch die Idee der Communities, die sich als neue Organisationsform von Benutzern elektronischer Kommunikationsmedien entwickelt haben, zu erweitern. Dazu werden am Beispiel des Schiffbaus aktuelle Fragestellungen diskutiert sowie ein Lösungsansatz für eine Collaborative Engineering Plattform vorgestellt. Darauf aufbauend wird der Community- Gedanke auf die Produktentwicklung übertragen; Anforderungen an Communities im Engineering-Bereich werden abgeleitet. Abschließend erfolgt die Beschreibung einer Rahmenarchitektur sowie die Formulierung von Forschungsfragen zur Realisierung von Collaborative Engineering Communities

ON THE DISCRETIZATION OF A BISTABLE CANTILEVER BEAM WITH APPLICATION TO ENERGY HARVESTING

A typical setup for energy harvesting is that of a cantilever beam with piezoceramics excited by ambient base vibrations. In order to get higher energy output for a wide range of excitation frequencies, often a nonlinearity is introduced by intention in that way, that two magnets are fixed close to the free tip of the beam. Depending on strength and position of the magnets, this can either result in a mono-, bi- or tristable system. In our study, we focus on a bistable system. Such systems have been investigated thoroughly in literature while in almost all cases the beam has been discretized by a single shape function, in general the first eigenshape of the linear beam with undeflected stable equilibrium position.There can be some doubts about the suitability of a discretization by a single shape function mainly due to two reasons. First: In case of stochastic broadband excitations a discretization, taking into consideration just the first vibration shape seems not to be reasonable. Second: as the undeflected position of the considered system is unstable and the system significantly nonlinear, the question arises, if using just one eigenshape of the linear beam is a suitable approximation of the operation shapes during excited oscillations even in the case of harmonic excitation. Are there other, e.g. amplitude dependent, possibilities and/or should multiple ansatz functions be considered instead?In this paper, we focus mainly on the second point. Therefore, a bistable cantilever beam with harmonic base excitation is considered and experimental investigations of operation shapes are performed using a high-speed camera. The observed operation shapes are expanded in a similar way as it is done in a theoretical analysis by a corresponding mixed Ritz ansatz. The results show the existence of distinct superharmonics (as one can expect for a nonlinear system) but additionally the necessity to use more than one shape function in the discretization, covering also the amplitude dependence of the observed operation shapes

Comparison of the dynamics of a Duffing equation model and experimental results for a bistable cantilever beam in magnetoelastic energy harvesting

Nonlinear energy harvesting systems, consisting of a piezo cantilever beam with two additional magnets placed near the beam’s free end, have received a lot of attention in the past decade. The most common approach to model this system is to discretize the beam in space with one modal ansatz function and to assume a cubic restoring force caused by the magnetic field. The magnets are positioned so that two stable equilibrium positions exist in addition to the unstable undeflected beam tip displacement, i.e. the system is bistable. This modeling procedure results in a Duffing equation with a negative linear and a positive cubic restoring term, which is capable to represent the bistability. However, its sufficiency is often just assumed without thorough experimental validation of the mentioned presumptions. In this paper the authors present the results of broad experimental investigations into the sufficiency of the Duffing equation as the underlying model of the mechanical subsystem (beam and magnets, but for the sake of simplicity without piezos). Therefore, a model is developed accordingly, following the approach of most publications, where a heuristic method is used to determine the cubic restoring force of the system. The theoretical predictions of the Duffing like model concerning the dynamical response to different harmonic base excitations are compared to experimental measurements done on a physical setup of the investigated system. The results are generally in good agreement, however particular limitations regarding the model are observed, as there is a shift of the occurring solutions to higher frequencies in the theoretical model compared to the experiments

An argon ion beam milling process for native AlOx\text{AlO}_\text{x} layers enabling coherent superconducting contacts

We present an argon ion beam milling process to remove the native oxide layer forming on aluminum thin films due to their exposure to atmosphere in between lithographic steps. Our cleaning process is readily integrable with conventional fabrication of Josephson junction quantum circuits. From measurements of the internal quality factors of superconducting microwave resonators with and without contacts, we place an upper bound on the residual resistance of an ion beam milled contact of 50$\,\mathrm{m}\Omega \cdot \mu \mathrm{m}^2$ at a frequency of 4.5 GHz. Resonators for which only $6\%$ of the total foot-print was exposed to the ion beam milling, in areas of low electric and high magnetic field, showed quality factors above $10^6$ in the single photon regime, and no degradation compared to single layer samples. We believe these results will enable the development of increasingly complex superconducting circuits for quantum information processing.Comment: 4 pages, 4 figures, supplementary materia