TY - JOUR AB - In applications of piezoelectric actuators and sensors, the dependability and particularly the reliability throughout their lifetime are vital to manufacturers and end-users and are enabled through condition-monitoring approaches. Existing approaches often utilize impedance measurements over a range of frequencies or velocity measurements and require additional equipment or sensors, such as a laser Doppler vibrometer. Furthermore, the non-negligible effects of varying operating conditions are often unconsidered. To minimize the need for additional sensors while maintaining the dependability of piezoelectric bending actuators irrespective of varying operating conditions, an online diagnostics approach is proposed. To this end, time- and frequency-domain features are extracted from monitored current signals to reflect hairline crack development in bending actuators. For validation of applicability, the presented analysis method was evaluated on piezoelectric bending actuators subjected to accelerated lifetime tests at varying voltage amplitudes and under external damping conditions. In the presence of a crack and due to a diminished stiffness, the resonance frequency decreases and the root-mean-square amplitude of the current signal simultaneously abruptly drops during the lifetime tests. Furthermore, the piezoelectric crack surfaces clapping is reflected in higher harmonics of the current signal. Thus, time-domain features and harmonics of the current signals are sufficient to diagnose hairline cracks in the actuators. AU - Aimiyekagbon, Osarenren Kennedy AU - Bender, Amelie AU - Hemsel, Tobias AU - Sextro, Walter ID - 51518 IS - 3 JF - Electronics KW - piezoelectric transducer KW - self-sensing KW - fault detection KW - diagnostics KW - hairline crack KW - condition monitoring SN - 2079-9292 TI - Diagnostics of Piezoelectric Bending Actuators Subjected to Varying Operating Conditions VL - 13 ER - TY - GEN AU - Sehlmeyer, Birte AU - Kampmann, Rebecca AU - Scheidemann, Claus AU - Hemsel, Tobias AU - Getzlaff, Mathias ID - 47234 T2 - Frühjahrstagung 2023, Sektion Kondensierte Materie (SKM) TI - Burst Mode of Ultrasonic Resonant Oscillations for Stimulation and Destruction of Tumor Cells ER - TY - GEN AU - Kampmann, Rebecca AU - Sehlmeyer, Birte AU - Scheidemann, Claus AU - Hemsel, Tobias AU - Getzlaff, Mathias ID - 47235 T2 - Frühjahrstagung 2023, Sektion Kondensierte Marterie (SKM) TI - Burst Mode Characteristics of an Ultrasonic Transducer for Treatment of Cancer Cells ER - TY - GEN AU - Scheidemann, Claus AU - Hemsel, Tobias AU - Friesen, Olga AU - Claes, Leander AU - Sextro, Walter ID - 51117 TI - Influence of Temperature and Pre-Stress on the Piezoelectric Material Behavior of Ring-Shaped Ceramics ER - TY - GEN AU - Scheidemann, Claus AU - Hemsel, Tobias AU - Friesen, Olga AU - Claes, Leander AU - Sextro, Walter ID - 51118 TI - Influence of Temperature and Pre-Stress on the Piezoelectric Material Behavior of Ring-Shaped Ceramics ER - TY - GEN AU - Scheidemann, Claus AU - Hagedorn, Oliver Ernst Caspar AU - Hemsel, Tobias AU - Sextro, Walter ID - 51119 TI - Experimental Investigation of Bond Formation and Wire Deformation in the Ultrasonic Wire Bonding Process ER - TY - CHAP AB - This article is dedicated to piezoelectric ultrasonic power transducers that differ to well known medical ultrasonic diagnostic apparatus or non destructive testing devices by the level of power in use; typically several tens of up to more than thousand watts are used in a multitude of different applications. After a short introduction including historical development, the first focus is on theoretical background of the operating principle, design and mechanical modeling. As piezoelectric elements transform electrical to mechanical energy and vice versa, equivalent circuit modeling is also described. After that, sample applications are delineated by the matter wherein ultrasound generates unique effects: incredible high pressure level as well in air as in water, micro-bubbles generating temperature peaks for very short time instances in fluids, acoustoplastic effect, enhancement of diffusion and recrystallization in solids, friction manipulation, incremental deformation and micro-cracking of surfaces, or even generation of macroscopic movements in motors. At the end, some future directions ranging from novel modeling approaches to advanced control and new materials are addressed. AU - Hemsel, Tobias AU - Twiefel, Jens ID - 33500 KW - Equivalent circuit model KW - Langevin transducer KW - Lumped parameter model KW - Piezoelectric transducer KW - Ultrasonic processes KW - Ultrasound SN - 978-0-12-803581-8 T2 - Reference Module in Materials Science and Materials Engineering TI - Piezoelectric Ultrasonic Power Transducers ER - TY - CONF AB - To achieve optimum bond results at ultrasonic bonding thick copper wire on sensitive components is quite challenging. Bearing in mind that high normal force and ultrasonic power are needed for bond quality but as well increase stress and finally failure risk of the substrate, methods should be found to achieve high bond quality even at lower bond parameters. Therefore, bond experiments with different bond tool grove geometries have been conducted for copper and aluminum wire on direct copper bonded (DCB) substrates to investigate the impact of geometric parameters on bond formation and bond quality. The wire material depending impact of geometry changes on the bond formation and deformation was quantified. Additionally, a bonding parameter design of experiments (DOE) has been conducted for the reference and the most promising groove geometry. Higher shear values were achieved at reduced vertical tool displacement for most bonding parameter combinations, compared to the reference tool. This behavior allows for reducing ultrasonic power to obtain equal shear values; consequently, mechanical stresses in the interface decrease. This could potentially reduce the risk of chip damage and thus yield loss. AU - Hagedorn, Oliver Ernst Caspar AU - Broll, Marian AU - Kirsch, Olaf AU - Hemsel, Tobias AU - Sextro, Walter ID - 30371 SN - ISBN 978-3-8007-5757-2 T2 - CIPS 2022 - 12th International Conference on Integrated Power Electronics Systems TI - Experimental Investigation of the Influence of different Bond Tool Grooves on the Bond Quality for Ultrasonic Thick Wire Bonding ER - TY - CONF AB - ue to the constantly growing energy demand of power electronics and the need to reduce the size of electronic components like power modules for e-mobility, new challenges arise for ultrasonic wire bonding: the electrical connection must endure higher thermal and mechanical stress while the connecting partners become more sensitive or require more energy to get bonded. Past investigations have shown already that multi-dimensional ultrasonic bonding and welding yield the same or even better bond quality while reducing the load on the components. This contribution is intended to show whether multidi-mensional thick wire bonding is a promising concept to over-come the new challenges. The focus is on experimental investi-gations of different bond tool trajectories in ultrasonic wire bonding of aluminum and copper wire on DCB's and chips. The bond quality is analyzed by shear tests, microsections and, in the case of aluminum bonding, by a new machine learning method for an objective automated evaluation of the sheared area. AU - Scheidemann, Claus AU - Kirsch, Olaf AU - Hemsel, Tobias AU - Sextro, Walter ID - 34104 T2 - 2022 IEEE 9th Electronics System-Integration Technology Conference (ESTC) TI - Experimental Investigation of Multidimensional Ultrasonic Heavy Wire Bonding ER - TY - GEN AU - Scheidemann, Claus AU - Hemsel, Tobias AU - Sextro, Walter ID - 52045 TI - Modellbasierte Ermittlung optimaler Prozessparameter für neuartige Ultraschallbondverbindungen ER - TY - JOUR AB - Ultrasonic wire bonding is a solid-state joining process, used in the electronics industry to form electrical connections, e.g. to connect electrical terminals within semiconductor modules. Many process parameters affect the bond strength, such like the bond normal force, ultrasonic power, wire material and bonding frequency. Today, process design, development, and optimization is most likely based on the knowledge of process engineers and is mainly performed by experimental testing. In this contribution, a newly developed simulation tool is presented, to reduce time and costs and efficiently determine optimized process parameter. Based on a co-simulation of MATLAB and ANSYS, the different physical phenomena of the wire bonding process are considered using finite element simulation for the complex plastic deformation of the wire and reduced order models for the transient dynamics of the transducer, wire, substrate and bond formation. The model parameters such as the coefficients of friction between bond tool and wire and between wire and substrate were determined for aluminium and copper wire in experiments with a test rig specially developed for the requirements of heavy wire bonding. To reduce simulation time, for the finite element simulation a restart analysis and high performance computing is utilized. Detailed analysis of the bond formation showed, that the normal pressure distribution in the contact between wire and substrate has high impact on bond formation and distribution of welded areas in the contact area. AU - Schemmel, Reinhard AU - Krieger, Viktor AU - Hemsel, Tobias AU - Sextro, Walter ID - 21436 JF - Microelectronics Reliability KW - Ultrasonic heavy wire bonding KW - Co-simulation KW - ANSYS KW - MATLAB KW - Process optimization KW - Friction coefficient KW - Copper-copper KW - Aluminium-copper SN - 0026-2714 TI - Co-simulation of MATLAB and ANSYS for ultrasonic wire bonding process optimization VL - 119 ER - TY - CONF AB - Ultrasonic wire bonding is a process to form electrical connections in electronics well established industry. Typically, a clamping tool is pressed on the wire and forced to vibrate at relative high frequency 40 to 100 kHz. The ultrasonic vibration is transmitted through the wire into the interface between wire and substrate. Due to frictional processes, contamination like oxide layers are removed from the contact zone, the surface roughness is reduced, and with increasing bond duration an metallic connection of wire and substrate is established. It is known that the amount of ultrasonic energy over time directly influences the strength and reliability of the bond connection, but the determination of optimum bond parameters is still a challenging experimental task. For this, in the past different model approaches have been presented, to calculate the bond quality by simulation. Measuring the friction between wire and substrate to validate these models is a challenging task at ultrasonic bonding frequency. Therefore a versatile test rig for bonding experiments at frequencies lower than 1 kHz is setup to get detailed insight into the different phases of the connection process. It includes a piezoelectric force sensor for the measurement of the three-dimensional process forces, an electrodynamic shaker for the vibration excitation and a conventional tension-compression testing machine to apply the bond normal force. Using this test rig, it is possible to observe the different phases of bond formation in detail, validate and enhance existing models and finally optimize bond parameters for different processes. AU - Schemmel, Reinhard AU - Scheidemann, Claus AU - Hemsel, Tobias AU - Kirsch, Olaf AU - Sextro, Walter ID - 17355 T2 - CIPS 2020; 11th International Conference on Integrated Power Electronics Systems TI - Experimental analysis and modelling of bond formation in ultrasonic heavy wire bonding ER - TY - CONF AU - Schemmel, Reinhard AU - Krieger, Viktor AU - Hemsel, Tobias AU - Sextro, Walter ID - 17706 SN - 9781728160498 T2 - 2020 21st International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE) TI - Co-simulation of MATLAB and ANSYS for ultrasonic wire bonding process optimization ER - TY - CONF AB - In a variety of industrial applications, liquids are atomized to produce aerosols for further processing. Example applications are the coating of surfaces with paints, the application of ultra-thin adhesive layers and the atomization of fuels for the production of combustible dispersions. In this publication different atomizing principles (standing-wave, capillary-wave, vibrating-mesh) are examined and discussed. Using an optimized standing-wave system, tough liquids with viscosities of up to about 100 Pas could be successfully atomized. AU - Dunst, Paul AU - Bornmann, Peter AU - Hemsel, Tobias AU - Littmann, Walter AU - Sextro, Walter ED - Lötters, Joost ED - Urban, Gerald ID - 14852 KW - atomization KW - ultrasound KW - standing-wave KW - capillarywave KW - vibrating-mesh T2 - Conference Proceedings - The 4th Conference on MicroFluidic Handling Systems (MFHS2019) TI - Atomization of Fluids with Ultrasound ER - TY - CONF AU - Hagedorn, Oliver Ernst Caspar AU - Pielsticker, Daniel AU - Hemsel, Tobias AU - Sextro, Walter ID - 15244 SN - 978-3-18-092366-6 T2 - 2. VDI-Fachtagung Schwingungen 2019 TI - Messung hochfrequenter In-Plane-Schwingungen mittels Laservibrometrie in räumlich eingeschränkten Umgebungen ER - TY - CONF AB - Für die Zerstäubung hochviskoser Flüssigkeiten werden neben Düsenzerstäubern vor allem UltraschallStehwellenzerstäuber angewendet [1]. Diese ermöglichen ohne weitere Maßnahmen zwar keine gerichtete Zerstäubung, benötigen jedoch im Gegensatz zu Düsenzerstäubern keine hohen Drücke und haben keine hohen Austrittsgeschwindigkeiten. Zur Erzeugung der Ultraschallwellen werden typischerweise piezoelektrische, mit Bolzen verschraubte LangevinWandler verwendet [1-4], die eine starke Schallabstrahlung bei einer elektrischen Eingangsleistung von bis zu einigen Kilowatt erzeugen können. Wie bei jedem anderen schwingenden System emittiert der Ultraschallwandler zunächst eine Wanderwelle. Mit einem Reflektor, der gegenüber der Sonotrode angeordnet ist, wird eine stehende Welle erzeugt. Im Resonanzabstand zwischen Reflektor und Wandler werden abgestrahlte und reflektierte Wellen so überlagert, dass höhere Schalldruckamplituden erzielt werden. Ein einfacher Ansatz zur Maximierung des Schallpegels im Stehwellenfeld ist die Erhöhung der Schwingungsamplituden des Wandlers, die jedoch zu Schäden oder zumindest zu einer Verringerung der Lebensdauer führen kann. Hohe Schalldrücke werden auch bei geringen Abständen zwischen Wandler und Reflektor erreicht. Das Volumen des Schallfeldes ist in diesem Fall jedoch für die meisten Prozesse zu klein. Ein weiterer Ansatz ist die Verwendung zweier entgegengesetzt angeordneter Wandler [5]. In diesem Fall erfordert jedoch die Erzeugung einer stehenden Welle eine genaue Abstimmung von Frequenz und Phase beider Wandler, was eine komplexe Steuerung erfordert. Ebenso ist es möglich, geometrische Randbedingungen des Stehwellensystems zu optimieren, sodass es zu optimaler Interferenz der Wellen kommt. Im Folgenden wird der Anschaulichkeit halber vereinfachend angenommen, dass der Wandler an seiner Sonotrodenoberfläche einzelne Schallstrahlen aussendet, die in Nähe des Wandlers nahezu parallel verlaufen und sich mit zunehmender Entfernung vom Wandler auffächern. Ein einfaches Stehwellensystem, bestehend aus ebener Sonotrode und ebenem Reflektor, erzeugt bei kleinem Abstand zwischen Sonotrode und Reflektor sehr hohe Schallpegel, da nahezu sämtliche ausgesandten Schallstrahlen in Richtung der Sonotrode reflektiert werden positive Interferenz entsteht. Erhöht man jedoch den Abstand zwischen Sonotrode und Reflektor, so nehmen die Verluste durch Schallstrahlen, die den Prozessraum verlassen, zu. Wie Abbildung 1 gezeigt, werden nur Schallstrahlen, die in etwa parallel zur Rotationsachse verlaufen, zum Wandler zurück reflektiert und tragen zum Stehwellenfeld bei. Die Strahlen haben zudem abhängig vom Abstrahlwinkel unterschiedliche Weglängen. Die Stehwellenbedingung ist demnach nur für Strahlen in der Nähe der Rotationsachse exakt erfüllt. Um dies zu vermeiden, müssen die Geometrien von Wandler und Reflektor optimiert werden. In den folgenden Abschnitten wird zunächst ein Optimierungsansatz vorgestellt. Mithilfe eines FiniteElemente-Modells werden die Auswirkungen einer optimierten Geometrie auf den maximalen Schalldruckpegel untersucht. Ergebnisse werden durch Messungen an einem experimentellen Aufbau eines Stehwellensystems validiert. Es wird gezeigt, wie sich die Optimierung der geometrischen Randbedingungen auf die Zerstäubung hochviskoser Flüssigkeiten auswirkt. AU - Dunst, Paul AU - Hemsel, Tobias AU - Bornmann, Peter AU - Littmann, Walter AU - Sextro, Walter ID - 10258 T2 - DAGA 2019 TI - Modellbasierte und experimentelle Charakterisierung von intensiven Ultraschall-Stehwellenfeldern für die Zerstäubung hochviskoser Flüssigkeiten ER - TY - JOUR AB - Ultrasonic joining is a common industrial process. In the electronics industry it is used to form electrical connections, including those of dissimilar materials. Multiple influencing factors in ultrasonic joining are known and extensively investigated; process parameters like ultrasonic power, bond force, and bonding frequency of the ultrasonic vibration are known to have a high impact on a reliable joining process and need to be adapted for each new application with different geometry or materials. This contribution is focused on increasing ultrasonic power transmitted to the interface and keeping mechanical stresses during ultrasonic bonding low by using a multi-dimensional ultrasonic transducer concept. Bonding results for a new designed connector pin in IGBT-modules achieved by multi- and one-dimensional bonding are discussed. AU - Schemmel, Reinhard AU - Hemsel, Tobias AU - Dymel, Collin AU - Hunstig, Matthias AU - Brökelmann, Michael AU - Sextro, Walter ID - 10334 JF - Sensors and Actuators A: Physical KW - Ultrasonic bonding KW - Ultrasonic welding KW - Multi-dimensional bonding KW - Complex vibration KW - Multi-frequent KW - Two-dimensional friction model SN - 0924-4247 TI - Using complex multi-dimensional vibration trajectories in ultrasonic bonding and welding VL - 295 ER - TY - JOUR AB - The handling of fine powders is an important task in modern production processes. However, as fine powders strongly tend to adhesion and agglomeration, their processing with conventional methods is difficult or impossible. Especially when processing small amounts of highly sensitive fine powders, conventional methods reach their technical limits. In process steps such as dosing, transport, and especially mixing of fine powders new methods are required. Apart from the well-known method of manipulating powder properties by adding chemical additives, this contribution aims at improving the handling of dry fine powders by using vibrations at different frequencies. Modules are presented, which enable the continuous dosing, the homogeneous mixing and the transport of dry fine powders. Finally, these modules are combined for the production of a homogeneous mixture of two dry fine powders. AU - Dunst, Paul AU - Bornmann, Peter AU - Hemsel, Tobias AU - Littmann, Walter. AU - Sextro, Walter ID - 9990 JF - ACTUATOR 2018; 16th International Conference on New Actuators TI - Vibration Assisted Dosing, Mixing and Transport of Dry Fine Powders ER - TY - JOUR AB - Abstract:Since fine powders tend strongly to adhesion and agglomeration, their processing withconventional methods is difficult or impossible. Typically, in order to enable the handling of finepowders, chemicals are added to increase the flowability and reduce adhesion. This contributionshows that instead of additives also vibrations can be used to increase the flowability, to reduceadhesion and cohesion, and thus to enable or improve processes such as precision dosing, mixing,and transport of very fine powders. The methods for manipulating powder properties are describedin detail and prototypes for experimental studies are presented. It is shown that the handling of finepowders can be improved by using low-frequency, high-frequency or a combination of low- andhigh-frequency vibration. AU - Dunst, Paul AU - Bornmann, Peter AU - Hemsel, Tobias AU - Sextro, Walter ID - 9991 JF - Actuators 2018, 7(2). KW - powder handling KW - flowability KW - dosing KW - transport KW - mixing KW - dispersion KW - piezoelectricactuators KW - vibrations TI - Vibration-Assisted Handling of Dry Fine Powders ER - TY - CONF AB - State-of-the-art industrial compact high power electronic packages require copper-copper interconnections with larger cross sections made by ultrasonic bonding. In comparison to aluminium-copper, copper-copper interconnections require increased normal forces and ultrasonic power, which might lead to substrate damage due to increased mechanical stresses. One option to raise friction energy without increasing vibration amplitude between wire and substrate or bonding force is the use of two-dimensional vibration. The first part of this contribution reports on the development of a novel bonding system that executes two-dimensional vibrations of a tool-tip to bond a nail- like pin onto a copper substrate. Since intermetallic bonds only form properly when surfaces are clean, oxide free and activated, the geometries of tool-tip and pin were optimised using finite element analysis. To maximize the area of the bonded annulus the distribution of normal pressure was optimized by varying the convexity of the bottom side of the pin. Second, a statistical model obtained from an experimental parameter study shows the influence of different bonding parameters on the bond result. To find bonding parameters with the minimum number of tests, the experiments have been planned using a D-optimal experimental design approach. AU - Dymel, Collin AU - Eichwald, Paul AU - Schemmel, Reinhard AU - Hemsel, Tobias AU - Brökelmann, Michael AU - Hunstig, Matthias AU - Sextro, Walter ID - 9992 KW - ultrasonic wire-bonding KW - bond-tool design KW - parameter identification KW - statistical engineering T2 - (Proceedings of 7th Electronics System-Integration Technology Conference, Dresden, Germany) TI - Numerical and statistical investigation of weld formation in a novel two-dimensional copper-copper bonding process ER - TY - CONF AB - Ultrasonic bonding and welding are common friction based approaches in the assembly of power electronics. Interconnections with cross-sections of 0.3 mm² up to 12 mm² made from copper are well suited in high power applications. For increasing friction energy, which is responsible for bond formation, a two-dimensional vibration approach is applied to newly developed interconnection pins. Using two-dimensional vibration for bonding requires identification of suitable bonding parameters. Even though simulation models of wire bonding processes exist, parameters for the two-dimensional pin-bonding process cannot be derived accurately yet. Within this contribution, a methodology and workflow for experimental studies identifying a suitable bond parameter space are presented. The results of a pre-study are used to set up an extensive statistical parameter study, which gives insights about the bond strength change due to bond process parameter variation. By evaluation of electrical data captured during bonding, errors biasing the resulting shear forces are identified. All data obtained during the experimental study is used to build a statistical regression model suitable for predicting shear forces. The accuracy of the regression model’s predictions is determined and the applicability to predict process parameters or validate simulation models is assessed. Finally, the influence of the tool trajectory on the bond formation is determined, comparing one dimensional, elliptic and circular trajectories. AU - Dymel, Collin AU - Schemmel, Reinhard AU - Hemsel, Tobias AU - Sextro, Walter AU - Brökelmann, Michael AU - Hunstig, Matthias ID - 9993 KW - ultrasonic two-dimensional bonding KW - electrical interconnection KW - process parameters T2 - (Proceedings of 8th Electronics IEEE CPMT Symposium Japan (ICSJ 2018), Kyoto, Japan) TI - Experimental investigations on the impact of bond process parameters in two-dimensional ultrasonic copper bonding ER - TY - CONF AB - Ultrasonic wedge/wedge-wire bonding is used to connect electrical terminals of semiconductor modules in power electronics. The wire is clamped with a tool by a normal force and ultrasonic vibration is transmitted through the wire into the interface between wire and substrate. Due to frictional processes contaminations like oxide layers are removed from the contact zone and the surface roughness is reduced, thus the real contact area is increased. In the next step of bond formation, thermomechanical forces create micro-junctions between the wire and substrate and the bond strength increases. The bond parameters like the bond normal force, the ultrasonic vibration amplitude and the geometry of the clamping tool show a high influence on the strength and reliability of the wire bond and need to be investigated in detail. Therefore, in this contribution the dynamical behaviour of the ultrasonic system, the wire and the substrate are modeled in form of substructures, which are connected by the friction contacts between tool and wire and between wire and substrate. Approaches for modelling the time variant contact behaviour, the substrate dynamics, and the model order reduction for a time efficient simulation are described to simulate the full bonding process. AU - Schemmel, Reinhard AU - Hemsel, Tobias AU - Sextro, Walter ID - 9998 T2 - 6th European Conference on Computational Mechanics (ECCM 6) TI - Numerical and experimental investigations in ultrasonic heavy wire bonding ER - TY - JOUR AB - The transportation of dry fine powders is an emerging technologic task, as in biotechnology, pharmaceu-tical and coatings industry the particle sizes of processed powders get smaller and smaller. Fine powdersare primarily defined by the fact that adhesive and cohesive forces outweigh the weight forces, leadingto mostly unwanted agglomeration (clumping) and adhesion to surfaces. Thereby it gets more difficult touse conventional conveyor systems (e.g. pneumatic or vibratory conveyors) for transport. A rather newmethod for transporting these fine powders is based on ultrasonic vibrations, which are used to reducefriction between powder and substrate. Within this contribution an experimental set-up consisting of apipe, a solenoid actuator for axial vibration and an annular piezoelectric actuator for the high frequencyradial vibration of the pipe is described. Since amplitudes of the radial pipe vibration should be as large aspossible to get high effects of friction reduction, the pipe is excited to vibrate in resonance. To determinethe optimum excitation frequency and actuator position the vibration modes and resonance frequenciesof the pipe are calculated and measured. Results are in good accordance. AU - Dunst, Paul AU - Hemsel, Tobias AU - Sextro, Walter ID - 9972 JF - elsevier KW - Powder transport Piezoelectrics Ultrasonics Pipe vibration Finite element simulation Fine powder TI - Analysis of pipe vibration in an ultrasonic powder transportationsystem VL - Sensors and Actuators A 263 ER - TY - CONF AB - Piezoelectric transducers are used in a wide range of applications. Reliability of these transducers is an important aspect in their application. Prognostics, which involve continuous monitoring of the health of technical systems and using this information to estimate the current health state and consequently predict the remaining useful lifetime (RUL), can be used to increase the reliability, safety, and availability of the transducers. This is achieved by utilizing the health state and RUL predictions to adaptively control the usage of the components or to schedule appropriate maintenance without interrupting operation. In this work, a prognostic approach utilizing self-sensing, where electric signals of a piezoelectric transducer are used as the condition monitoring data, is proposed. The approach involves training machine learning algorithms to model the degradation of the transducers through a health index and the use of the learned model to estimate the health index of similar transducers. The current health index is then used to estimate RUL of test components. The feasibility of the approach is demonstrated using piezoelectric bimorphs and the results show that the method is accurate in predicting the health index and RUL. AU - Kimotho, James Kuria AU - Sextro, Walter AU - Hemsel, Tobias ID - 9978 KW - Estimation of Remaining Useful Lifetime of Piezoelectric Transducers Based on Self-Sensing T2 - IEEE Transactions on Reliability TI - Estimation of Remaining Useful Lifetime of Piezoelectric Transducers Based on Self-Sensing ER - TY - CONF AB - ln der industriellen Fertigung werden zum Transport von Bauteilen häufig Förderketten genutzt. Obwohl die Förderketten meist nicht direkt mit den Arbeitsmedien in Berührung kommen, werden sie indirekt durch vagabundierende Stäube und Pulver, die an der geölten Kette anhaften, im Laufe der Zeit stark verschmutzt. Ein derart im Betrieb verschmutztes Kettenglied ist in Abbildung 1 dargestellt. Um die Lebensdauer der Ketten zu erhöhen und das Herunterfallen von Schmutzpartikel auf die Produkte zu vermeiden, muss die Kette regelmäßig gereinigt werden. Ziel des hier beschriebenen Forschungsvorhabens ist die Entwicklung eines Systems, das in der Lage ist, ein einzelnes Kettenglied in unter 60 s mittels Ultraschall zu reinigen. In [1] wurde in ersten Versuchen nachgewiesen, dass Stabschwinger in Abhängigkeit des Sonotrodenabstands zum Reinigungsobjekt und der Ultraschallamplitude eine intensive Reinigungswirkung entfalten. Das Konzept der Reinigungsanlage sieht deshalb vor, im ersten Schritt die stark verschmutzten Kettenglieder durch ein hochintensives Kavitationsfeld von direkt eingetauchten Stabschwingern vorzureinigen und anschließend schwer zugängliche Be- reiche wie Hinterschneidungen oder Bohrungen mittels konventioneller Tauchschwinger von Verschmutzungen zu befreien. Für den Stabschwinger wird die sogenannte - Sonotrode untersucht; diese wird unter anderem auch in der Sonochemie verwendet. Ein wesentliches Merkmal der Sonotrode ist eine hohe Amplitudenübersetzung bei einer gleichzeitig großen Abstrahlfläche. Neben dem Entwurf mittels der L /2 -Synthese wird die Reinigungswirkung der Sonotrode in Abhängigkeit der Ultraschallamplitude und dem Abstand zum Reinigungsobjekt in einer Versuchsreihe untersucht. Zur genaueren Betrachtung der Reinigungs- mechanismen eines Stabschwingers werden abschließend Hochgeschwindigkeitsaufnahmen vorgestellt und analysieren. AU - Schemmel, Reinhard AU - Hemsel, Tobias AU - Sextro, Walter ID - 9982 KW - wire bonding KW - dynamic behavior KW - modeling T2 - 43. Deutsche Jahrestagung für Akustik TI - MoRFUS: Mobile Reinigungseinheit für Förderketten basierend auf Ultraschall ER - TY - CONF AB - The transportation of dry fine powders is an emerging technologic task, as in biotechnology, pharmaceutical or coatings industry particle sizes of processed powders are getting smaller and smaller. Fine powders are primarily defined by the fact that adhesive and cohesive forces outweigh the weight forces. This leads to mostly unwanted agglomeration (clumping) and adhesion to surfaces, what makes it more difficult to use conventional conveyor systems (e. g. pneumatic or vibratory conveyors) for transport. A rather new method for transporting these fine powders is based on ultrasonic vibrations, which are used to reduce friction and adhesion between powder and the substrate. One very effective set-up consists of a pipe, which vibrates harmoniously in axial direction at low frequency combined with a pulsed radial high frequency vibration. The high frequency vibration accelerates the particles perpendicular to the surface of the pipe, which in average leads to lower normal and thereby smaller friction force. With coordinated friction manipulation the powder acceleration can be varied so that the powder may be greatly accelerated and only slightly decelerated in each excitation period of the low frequency axial vibration of the pipe. The amount of powder flow is adjustable by vibration amplitudes, frequencies, and pulse rate, which makes the device versatile for comparable high volume and fine dosing using one setup. Within this contribution an experimental set-up consisting of a pipe, a solenoid actuator for axial vibration and a piezoelectric actuator for the radial high frequency vibration is described. An analytical model is shown, that simulates the powder velocity. Finally, simulation results are validated by experimental data for different driving parameters such as amplitude of low frequency vibration, pipe material and inclination angle. AU - Dunst, Paul AU - Sextro, Walter AU - Bornmann, Peter AU - Hemsel, Tobias AU - Littmann, Walter ID - 9958 T2 - PAMM Proc. Appl. Math. Mech. 16 TI - Transportation of dry fine powders by coordinated friction manipulation ER - TY - JOUR AB - Eine Vielzahl von Prozessen in der Chemie und Verfahrenstechnik kann durch Ultraschall positiv beeinflusst werden. Oftmals ist ultraschallinduzierte Kavitation der Hauptwirkmechanismus für die positiven Effekte der Beschallung. Daher ist es notwendig die Kavitationsaktivität während des Prozesses zu quantifizieren um die Beschallung für den jeweiligen Prozess optimal gestalten und überwachen zu können. Eine Möglichkeit der prozessbegleitenden Kavitationsdetektion ist die Auswertung der akustischen Emissionen von oszillierenden und kollabierenden Kavitationsblasen mittels Drucksensoren in der Flüssigkeit. Raue Prozessrandbedingungen wie hohe Temperaturen oder aggressive Flüssigkeiten erschweren es jedoch geeignete Sensoren zu finden. Als Alternative wurde daher die Nutzbarkeit der Rückwirkung von Kavitationsereignissen auf das elektrische Eingansgssignal des Ultraschallwandlers zur Quantifizierung von Kavitation untersucht. Die experimentelle Analyse hat ergeben, dass das Einsetzen und in einigen Fällen auch die Art der Kavitation auf Basis der Rückwirkung auf das Stromsignal des Ultraschallwandlers bestimmt werden kann. Die Stärke der Kavitation war hingegen nicht aus den Stromsignalen abzuleiten. AU - Bornmann, Peter AU - Hemsel, Tobias AU - Sextro, Walter AU - Memoli, Gianluca AU - Hodnett, Mark AU - Zeqiri, Bajram ID - 9944 IS - 2 JF - tm - Technisches Messen KW - Kavitationsdetektion KW - Self-Sensing KW - So- nochemie KW - Ultraschallwandler TI - Kavitationsdetektion mittels Self-Sensing-Ultraschallwandler VL - 82 ER - TY - JOUR AU - Kudo, Ryo AU - Bornmann, Peter AU - Hemsel, Tobias AU - Morita, Takeshi ID - 9948 IS - 3 JF - Acoustical Science and Technology TI - Thick KNbO 3 films deposited by ultrasonic-assisted hydrothermal method VL - 36 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 - 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 - JOUR AB - A piezoelectric cantilever beam with a tip mass at its free end is a common energy harvester configuration. This article introduces a new principle of designing such a harvester that increases the generated power without changing the resonance frequency of the harvester: the attraction force between two permanent magnets is used to add stiffness to the system. This magnetic stiffening counters the effect of the tip mass on the efficient operation frequency. Five set-ups incorporating piezoelectric bimorph cantilevers of the same type in different mechanical configurations are compared theoretically and experimentally to investigate the feasibility of this principle: theoretical and experimental results show that magnetically stiffened harvesters have important advantages over conventional set-ups with and without tip mass. They generate more power while only slightly increasing the deflection in the piezoelectric harvester and they can be tuned across a wide range of excitation frequencies. AU - Al-Ashtari, Waleed AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9794 IS - 11 JF - Journal of Intelligent Material Systems and Structures TI - Increasing the power of piezoelectric energy harvesters by magnetic stiffening VL - 24 ER - TY - JOUR AB - Power and bandwidth of piezoelectric harvesters can be increased by using multiple piezoelectric elements in one harvester. In this contribution, a novel energy harvesting cantilever array with magnetic tuning including three piezoelectric bimorphs is investigated theoretically and experimentally, with a good agreement between model and experiment. Other than harvester designs proposed before, this array is easy to manufacture and insensitive to manufacturing tolerances because its optimum operation frequency can be re-adjusted after fabrication. Using the superposition principle, the Butterworth-Van Dyke model and a mechanical lumped parameters model, the generated voltage and current are determined analytically. Formulas for calculating the power generated by array harvesters with an arbitrary number of piezoelectric elements connected in series or in parallel are derived. It is shown that optimum harvester design must take both the connected load and the operating frequency into account. Strategies for connecting multiple bimorphs to increase the maximum generated power and/or enhance the bandwidth compared to a single bimorph harvester are investigated. For bandwidth enhancement it is essential that individual rectifiers are used for the bimorphs. An example with three bimorphs shows that, depending on the chosen tuning strategy, the power is increased by about 340\% or the bandwidth is increased by about 500\%, compared to one single bimorph. AU - Al-Ashtari, Waleed AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9795 JF - Sensors and Actuators A: Physical KW - Energy harvesting KW - Cantilever array KW - Bandwidth KW - Power increase TI - Enhanced energy harvesting using multiple piezoelectric elements: Theory and experiments VL - 200 ER - TY - CONF AB - A basic autonomous system powered by a piezoelectric harvester contains three components apart from the harvester: a fullwave rectifier, a reservoir capacitor and an electronic device performing the primary task of the system. In this contribution, a model describing the operation of such a system is derived. It is found that in steady-state operation, the piezoelectric harvester experiences two alternating load conditions due to the rectification process. These alternating load conditions can have a significant effect on the operation of the harvester and must be considered in the design of autonomous systems. The results also show that such an autonomous system works efficiently if it is connected to a high impedance load and excited by a frequency matching the anti-resonance frequency of the piezoelectric harvester. AU - Al-Ashtari, Waleed AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9796 IS - 05/2013 KW - Energy harvesting KW - harvester modeling KW - load dependence KW - generated voltage T2 - Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop, Hannover, Germany, 14.-17.7.2013 TI - Characteristics of Piezoelectric Energy Harvesters in Autonomous Systems ER - TY - CONF AB - A model approach for wedge/wedge bonding copper wire is presented. The connection between wire and substrate is based on a variety of physical effects, but the dominant one is the friction based welding while applying ultrasound. Consequently, a friction model was used to investigate the welding process. This model is built up universal and can be used to describe the formation of micro welds in the time variant contact area between wire and substrate. Aim of the model is to identify the interactions between touchdown, bond normal force, ultrasonic power and bonding time. To do so, the contact area is discretized into partial areas where a Point Contact Model is applied. Based on this approach it is possible to simulate micro and macro slip inside the contact area between wire and substrate. The work done by friction force is a main criterion to define occurring micro joints which influence the subsequent welding. AU - Althoff, Simon AU - Neuhaus, Jan AU - Hemsel, Tobias AU - Sextro, Walter ID - 9797 KW - Wire bonding KW - friction modeling KW - wire bond quality KW - contact element modeling T2 - IMAPS 2013, 46th International Symposium on Microelectronics TI - A friction based approach for modeling wire bonding ER - TY - CONF AU - Hunstig, Matthias AU - Al-Ashtari, Waleed AU - Hemsel, Tobias AU - Sextro, Walter ED - Gausemeier, Jürgen ED - Dumitrescu, Roman ED - Rammig, Franz ED - Schäfer, Wilhelm ED - Trächtler, Ansgar ID - 9801 T2 - 9. Paderborner Workshop Entwurf mechatronischer Systeme TI - Leistungs- und Bandbreitensteigerung von Energy-Harvesting-Generatoren für Energieautarke Systeme ER - TY - CONF AB - It has been shown previously that ``slip-slip'' operation of piezoelectric inertia motors allows higher velocities and smoother movements than classic ``stick-slip'' operation. One very promising driving option is to use a superposition of multiple sinusoidal signals. In this contribution, previous theoretical results are validated experimentally. The results confirm the theoretical result that for a given maximum frequency, usually defined by the actuator characteristics, a signal with high fundamental frequency and consisting of two superposed sine waves leads to the highest velocity and the smoothest motion. This result is of fundamental importance for the further development of high-velocity piezoelectric inertia motors. AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9802 KW - Piezoelectric inertia motor KW - stick-slip motor KW - driving signal KW - velocity KW - smoothness T2 - Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop TI - High-Velocity Slip-Slip Operation of Piezoelectric Inertia Motors - Experimental Validation ER - TY - JOUR AB - Piezoelectric inertia motors, also known as stickslip drives or (smooth) impact drives, use the inertia of a body to drive it by a friction contact in small steps, in the majority of motors composed of a stick phase and a slip phase between the friction partners. For optimizing inertia motors, it is important to understand the friction contact correctly and to measure its properties appropriately. This contribution presents experimental set-ups for measuring the contact force, friction force and relative displacement in an actual inertia motor with a dry friction contact and numerical simulations of the motor operation. The motor uses a pre-stressed multilayer actuator with a displacement in the range of 20 $\mu$ m. It is shown that a previously postulated condition for the applicability of simple kinetic friction models is well fulfilled for the investigated motor. The friction contact in the motor is simulated using different kinetic friction models. The input for the friction models is the measured motion of the rod. The models qualitatively reproduce the measured motion but show quantitative deviations varying with frequency. These can be explained by vibrations of the driving rod that are experimentally investigated. AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9803 IS - 11 JF - Journal of Intelligent Material Systems and Structures KW - Actuator KW - friction KW - motor KW - piezoelectric TI - Modelling the friction contact in an inertia motor VL - 24 ER - TY - JOUR AB - This contribution provides a systematic investigation and performance comparison of different modes of operation for piezoelectric inertia drives. The movement of these motors is classically assumed to consist of steps involving stiction and sliding, resulting in the term ``stick-slip drives''. In the first part of this contribution it has been found that using ideal driving signals, ``slip-slip'' operation without phases of stiction allows very high velocities, while the maximum velocity is limited principally in stick-slip operation. In this part it is shown that slip-slip operation is also suitable for use with real actuators, driven with frequency-limited versions of the ideal signals presented in part I. The motional performance of the motor as well as its wear and the required electric power are investigated for operation with different signals. It is found that for high velocity inertia motors it is recommendable to use actuators with large stroke and to drive them with a signal consisting of two harmonics at a high fundamental frequency, a result that is supported by similar setups implemented experimentally by other authors. Using Lanczos' \sigma factors to calculate the frequency-limited excitation signals instead of standard Fourier series additionally increases the motor performance significantly. The results help motor designers to choose the appropriate mode of operation and to optimise the motor parameters for their individual applications. AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9804 JF - Sensors and Actuators A: Physical KW - Inertia motor TI - Stick-slip and slip-slip operation of piezoelectric inertia drives - Part II: Frequency-limited excitation VL - 200 ER - TY - JOUR AB - Piezoelectric inertia motors, also known as ``stick--slip drives'', use the inertia of a body to drive it in small steps by means of a friction contact. While these steps are classically assumed to involve stiction and sliding, the motors can also operate in ``slip--slip'' mode without any phase of static friction. This contribution provides a systematic investigation and performance comparison of different stick--slip and slip--slip modes of operation. Different criteria for comparing the motional performance of inertia motors are defined: Steady state velocity, smoothness of motion, and start-up time. Using the example of a translational inertia motor excited by an ideal displacement signal, it is found that the maximum velocity reachable in stick--slip operation is limited principally, while continuous slip--slip operation allows very high velocities. For the investigated driving signals, the motor velocity is proportional to the square root of the actuator stroke. The motor performance with these ideal signals defines an upper boundary for the performance of real motors. AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9805 JF - Sensors and Actuators A: Physical KW - Inertia motor KW - Stick--slip drive KW - Mode of operation KW - Performance indicator KW - Velocity maximization KW - Actuator stroke TI - Stick-slip and slip-slip operation of piezoelectric inertia drives - Part I: Ideal Excitation. VL - 200 ER - TY - JOUR AB - The hydrothermal method utilizes a solution-based chemical reaction to synthesize piezoelectric thin films and powders. This method has a number of advantages, such as low-temperature synthesis, and high purity and high quality of the product. In order to promote hydrothermal reactions, we developed an ultrasonic assisted hydrothermal method and confirmed that it produces dense and thick lead--zirconate--titanate (PZT) films. In the hydrothermal method, a crystal growth process follows the nucleation process. In this study, we verified that ultrasonic irradiation is effective for the nucleation process, and there is an optimum irradiation period to obtain thicker PZT films. With this optimization, a 9.2-$\mu$ m-thick PZT polycrystalline film was obtained in a single deposition process. For this film, ultrasonic irradiation was carried out from the beginning of the reaction for 18 h, followed by a 6 h deposition without ultrasonic irradiation. These results indicate that the ultrasonic irradiation mainly promotes the nucleation process. AU - Ohta, Kanako AU - Isobe, Gaku AU - Bornmann, Peter AU - Hemsel, Tobias AU - Morita, Takeshi ID - 9866 IS - 4 JF - Ultrasonics KW - Piezoelectric material SN - 0041-624X TI - Study on optimizing ultrasonic irradiation period for thick polycrystalline PZT film by hydrothermal method VL - 53 ER - TY - JOUR AB - We report the piezoelectric properties of CuO-doped hydrothermal (K,Na)NbO3 ceramics that can be applied as hard-type lead-free piezoelectric ceramics. To date, we have succeeded in synthesizing high-quality KNbO3 and NaNbO3 powders by the hydrothermal method, which is based on an ionic reaction at high temperature (around 210 $\,^{\circ}$C) and pressure. Increasing both the piezoelectric constant d and the mechanical quality factor (Qm) is important for resonance-type piezoelectric devices, such as ultrasonic motors and transformers. CuO doping into hydrothermal (K,Na)NbO3 ceramics was examined to realize hard-type lead-free piezoelectric ceramics. By doping with 1.2 mol \% CuO, Qm was increased and the dielectric loss (tan δ) was decreased to 0.5\%. The grain size was also influenced by the amount of CuO doping, which indicates that Qm is related to the density. To achieve a higher Qm value, the grain size is required to be less than 5 µm; however, excessive CuO doping leads to anomalous grain growth. Optimal piezoelectric properties were obtained for 1.2 mol \% CuO-doped (K,Na)NbO3; k31 = 0.32, d31 = -44 pC/N, Qm (radial) = 959, and tan δ= 0.5\%. These characteristics showed that CuO doping with hydrothermal powders is effective for obtaining hard-type ceramics, and the mechanical quality factor is more than ten times higher than that of nondoped hydrothermal (K,Na)NbO3 ceramics. Therefore, compared with the conventional solid-state method, we could succeed in obtaining hard-type ceramics by a simple and short process. AU - Yokouchi, Yuriko AU - Maeda, Takafumi AU - Bornmann, Peter AU - Hemsel, Tobias AU - Morita, Takeshi ID - 9867 IS - 7S JF - Japanese Journal of Applied Physics TI - Piezoelectric Properties of CuO-Doped (K,Na)NbO3 Lead-Free Ceramics Synthesized with Hydrothermal Powders VL - 52 ER - TY - JOUR AB - A piezoelectric energy harvester is an electromechanical device that converts ambient mechanical vibration into electric power. Most existing vibration energy harvesting devices operate effectively at a single frequency only, dictated by the design of the device. This frequency must match the frequency of the host structure vibration. However, real world structural vibrations rarely have a specific constant frequency. Therefore, piezoelectric harvesters that generate usable power across a range of exciting frequencies are required to make this technology commercially viable. Currently known harvester tuning techniques have many limitations, in particular they miss the ability to work during harvester operation and most often cannot perform a precise tuning. This paper describes the design and testing of a vibration energy harvester with tunable resonance frequency, wherein the tuning is accomplished by changing the attraction force between two permanent magnets by adjusting the distance between the magnets. This tuning technique allows the natural frequency to be manipulated before and during operation of the harvester. Furthermore the paper presents a physical description of the frequency tuning effect. The experimental results achieved with a piezoelectric bimorph fit the calculated results very well. The calculation and experimental results show that using this tuning technique the natural frequency of the harvester can be varied efficiently within a wide range: in the test setup, the natural frequency of the piezoelectric bimorph could be increased by more than 70\%. AU - Al-Ashtari, Waleed AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9781 IS - 3 JF - Smart Materials and Structures TI - Frequency tuning of piezoelectric energy harvesters by magnetic force VL - 21 ER - TY - JOUR AB - Piezoelectric structures are nowadays used in many different applications. A better understanding of the influence of material properties and geometrical design on the performance of these structures helps to develop piezoelectric structures specifically designed for their application. Different equivalent circuits have been introduced in the literature to investigate the behaviour of piezoelectric transducers. The model parameters are usually determined from measurements covering the characteristic frequencies of the piezoelectric transducer. This article introduces an analytical technique for calculating the mechanical and electrical equivalent system parameters and characteristic frequencies based on material properties and geometry for a cantilever bimorph structure. The model is validated by measurements using a cantilever bimorph and fits the experimental results better than previous models. The model gives a full set of piezoelectric transducer parameters and is therefore well suited for further theoretical investigations of piezoelectric transducers for different applications. The results also show that even small manufacturing tolerances have a considerable effect on the system parameters and characteristic frequencies. This might lead to intolerable deviations, especially in dynamic applications and should be avoided by careful design and production. AU - Al-Ashtari, Waleed AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9782 IS - 1 JF - Journal of Intelligent Material Systems and Structures TI - Analytical determination of characteristic frequencies and equivalent circuit parameters of a piezoelectric bimorph VL - 23 ER - TY - CONF AB - To optimize the ultrasound irradiation for cavitation based ultrasound applications like sonochemistry or ultrasound cleaning, the correlation between cavitation intensity and the resulting effect on the process is of interest. Furthermore, changing conditions like temperature and pressure result in varying acoustic properties of the liquid. That might necessitate an adaption of the ultrasound irradiation. To detect such changes during operation, process monitoring is desired. Labor intensive processes, that might be carried out for several hours, also require process monitoring to increase their reliability by detection of changes or malfunctions during operation. In some applications cavitation detection and monitoring can be achieved by the application of sensors in the sound field. Though the application of sensors is possible, this necessitates modifications on the system and the sensor might disturb the sound field. In other applications harsh, process conditions prohibit the application of sensors in the sound field. Therefore alternative techniques for cavitation detection and monitoring are desired. The applicability of an external microphone and a self-sensing ultrasound transducer for cavitation detection were experimentally investigated. Both methods were found to be suitable and easily applicable. AU - Bornmann, Peter AU - Hemsel, Tobias AU - Sextro, Walter AU - Maeda, Takafumi AU - Morita, Takeshi ID - 9783 KW - cavitation KW - chemical reactors KW - microphones KW - process monitoring KW - reliability KW - ultrasonic applications KW - ultrasonic waves KW - acoustic properties KW - cavitation based ultrasound applications KW - cavitation intensity KW - change detection reliability KW - external microphone KW - malfunction detection reliability KW - nonperturbing cavitation detection KW - nonperturbing cavitation monitoring KW - process monitoring KW - self-sensing ultrasound transducer KW - sonochemical reactors KW - sonochemistry KW - ultrasound cleaning KW - ultrasound irradiation KW - Acoustics KW - Liquids KW - Monitoring KW - Sensors KW - Sonar equipment KW - Transducers KW - Ultrasonic imaging SN - 1948-5719 T2 - Ultrasonics Symposium (IUS), 2012 IEEE International TI - Non-perturbing cavitation detection / monitoring in sonochemical reactors ER - TY - CONF AB - Hydrothermal method enables to synthesize high quality piezoelectric materials. To shorten the reaction time and to get higher quality materials, we propose an ultrasonic irradiation to the solution during the hydrothermal method. We named it ultrasonic assisted hydrothermal method (UAHTM). We have synthesized lead-free piezoelectric material and PZT thin film and the effect of UAHTM have been confirmed. In this study, we tried to improve UAHTM. First, to generate powerful and stable ultrasonic irradiation at high temperature on UAHTM, we developed a new transducer using LiNbO3 single crystal. Second, to prevent contamination to the materials, A Teflon cover on the tip of transducer was attached. AU - Isobe, Gaku AU - Ageba, Ryo AU - Maeda, Takafumi AU - Bornmann, Peter AU - Hemsel, Tobias AU - Morita, Takeshi ED - B. J. Linde, Bogumil ED - Paczkowski, Jacek ED - Ponikwicki, Nikodem ID - 9785 IS - 1 KW - contamination KW - lead compounds KW - piezoelectric materials KW - piezoelectric thin films KW - piezoelectric transducers KW - ultrasonic effects T2 - AIP Conference Proceedings TI - Synthesis of piezoelectric materials by ultrasonic assisted hydrothermal method VL - 1433 ER - TY - CONF AB - A hydrothermal method utilizes a crystallization process in the solution so that the pure and high-quality powders can be realized. Sintering from the hydrothermal KNbO3 and NaNbO3 powders, a high-dense lead-free piezoelectric (K,Na)NbO3 ceramics could be obtained (density: 98.8\%). Concerning about the g33 constant, high value as large as commercial PZT ceramics was measured. Therefore, the hydrothermal (K,Na)NbO3 ceramics is usable for the sensors and the energy harvesting devices. To demonstrate the (K,Na)NbO3 ceramics, a hydrophone sensor was fabricated and evaluated. AU - Maeda, Takafumi AU - Bornmann, Peter AU - Hemsel, Tobias AU - Morita, Takeshi ID - 9788 KW - crystallisation KW - hydrophones KW - piezoceramics KW - potassium compounds KW - powder technology KW - powders KW - sensors KW - sintering KW - sodium compounds KW - (K0.48Na0.52)NbO3 KW - KNbO3 powder KW - NaNbO3 powder KW - crystallization KW - energy harvesting devices KW - g33 constant KW - hydrophone sensor KW - hydrothermal lead-free (K0.48Na0.52)NbO3 ceramics KW - hydrothermal method KW - piezoelectric applications KW - sintering KW - Materials KW - Transducers SN - 1948-5719 T2 - Ultrasonics Symposium (IUS), 2012 IEEE International TI - Piezoelectric applications of hydrothermal lead-free (K0.48Na0.52)NbO3 ceramics ER - TY - JOUR AB - [$Li_x(Na_0.52K_0.48)_1-x]NbO_3 (0 \leq x \leq 0.091)$ ceramics were synthesized using hydrothermal powders and the lithium doping content was controlled to optimize their piezoelectric properties. The raw KNbO$_3$ and NaNbO$_3$ powders were obtained separately by a hydrothermal method and LiNbO$_3$ powders were prepared by milling a commercial LiNbO$_3$ single crystal. These powders were mixed with ethanol at a molar ratio LiNbO$_3$: ($Na_0.52K_0.48$)NbO$_3 = x : 1-x$. The synthesized powders were sintered at 1060--1120 $\,^{\circ}$C for 2 h. We succeeded in obtaining highly dense [$Li_x(Na_0.52K_0.48)_1-x]NbO_3$ ceramics using hydrothermal powder. The X-ray diffraction patterns revealed that the crystal phase changed from orthorhombic to tetragonal at around x = 0.06. At this morphotropic phase boundary (MPB), the c/a ratio changed from 1.016 to 1.024 and the highest piezoelectric constant was obtained with the chemical component of [$Li_x(Na_0.52K_0.48)_1-x]NbO_3$. The obtained piezoelectric properties were as follows: $k_33 = 0.51, \epsilon 33^T/ \epsilon _0 = 836$ , $c_33^E = 46$ GPa, $d_33 = 203$ pC/N, and $T_c = 482 $\,^{\circ}$C$. AU - Maeda, Takafumi AU - Hemsel, Tobias AU - Morita, Takeshi ID - 9789 JF - Japanese Journal of Applied Physics TI - Piezoelectric Properties of Li-Doped (K0.48Na0.52)NbO3 Ceramics Synthesized Using Hydrothermally-Derived KNbO3 and NaNbO3 Fine Powders VL - 51 ER - TY - JOUR AB - Piezoelectric inertia motors, also known as ``stick-slip-drives'', use the inertia of a body to drive it by means of a friction contact in small steps. While these steps normally involve stiction and sliding, the motors can also operate in ``slip-slip'' mode without any phase of static friction. In this contribution, a one degree of freedom model of an inertia motor driven by an ideal actuator is analysed. Start-up and constant velocity operation of the motor are investigated and appropriate quantities to compare ``stick-slip'' and ``slip-slip'' operation are determined. Different aspects such as velocity, uniformity of motion, load capacity, robustness, efficiency, and wear are considered. The analysis allows both modes to be applied advantageously in different applications and can widen the field of application of piezoelectric inertia motors. Motor designers are enabled to choose the appropriate mode of operation and the best drive parameters for their individual applications. AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9806 JF - ACTUATOR 2012 Conference Proceedings KW - Piezoelectric Inertia Motors KW - Drive Signals KW - Stick-slip KW - Slip-slip TI - Analysis of different operation modes for inertia motors ER - TY - JOUR AB - The multi-objective optimal design of a piezoelectric sandwich ultrasonic transducer is studied. The maximum vibration amplitude and the minimum electrical input power are considered as optimization objectives. Design variables involve continuous variables (dimensions of the transducer) and discrete variables (material types). Based on analytical models, the optimal design is formulated as a constrained multi-objective optimization problem. The optimization problem is then solved by using the elitist non-dominated sorting genetic algorithm (NSGA-II) and Pareto-optimal designs are obtained. The optimized results are analyzed and the preferred design is proposed. The optimization procedure presented in this contribution can be applied in multi-objective optimization problems of other piezoelectric transducers. AU - Hemsel, Tobias AU - Fu, Bo AU - Jing, Yi AU - Fu, Xuan ID - 9765 JF - Key Engineering Materials TI - Multi-Objective Optimization of a Piezoelectric Sandwich Ultrasonic Transducer by Using Elitist Non-Dominated Sorting Genetic Algorithm VL - 474 - 476 ER - TY - JOUR AB - The paper presents the results of numerical and experimental investigation of cylindrical piezoelectric actuator used for achieving independent three degrees of freedom oscillations of the contact point. The design of actuator based on a hollow piezoelectric cylinder mounted on a metal rod. The piezoceramic cylinder has a radial polarization and special configuration of the electrodes that cover inner and outer surface of the cylinder. The main advantage of actuator's design is that solid metallic rod operates as a part of inner electrode of the cylinder and a stator of actuator. The geometry of piezoelectric actuator was adopted to reach resonance of oscillations for the first longitudinal mode and the third flexural mode at same frequency. The actuator is designed to move positioned object through contact point which is located on the top of the rod. The optimal topology of electrodes was found to achieve longitudinal and flexural oscillations of the actuator in two perpendicular planes. Three degrees of freedom of the positioning object can be achieved and control of the system can be implemented by applying different excitation schemes and regimes. The numerical simulation and experimental study of piezoelectric actuator was performed. Impedance of actuator was analyzed under different excitation regimes. The results of numerical modeling and experimental study were compared. Recommendations for the further development of this type of actuator are given. AU - Lucinskis, Raimundas AU - Mazeika, Dalius AU - Hemsel, Tobias AU - Bansevicius, Ramutis ID - 9767 IS - 1 JF - AIP Conference Proceedings KW - dielectric polarisation KW - piezoceramics KW - piezoelectric actuators TI - Multi-DOF cylindrical piezoelectric actuator with radial polarization VL - 1433 ER - TY - JOUR AB - In this study, we report some improvements in a hydrothermal method for lead-free piezoelectric powders and the performance of the sintered (K$_{0.48}$Na$_{0.52}$)NbO$_{3}$ ceramics. To increase the obtained powder weight per source solution volume, the hydrothermal reaction conditions were modified. This improvement is important for mass production; however, it resulted in a larger particle size dispersion. Therefore, we examined to introduced the ball milling process that is useful for dense (K$_{0.48}$Na$_{0.52}$)NbO$_{3}$ ceramics. When a large amount of powder was obtained, it took a long time to eliminate the residual alkaline ions in the hydrothermal powders by a washing process. Therefore, a neutralization was conducted in the powder washing process. Using this powder, a solid solution of (K,Na)NbO$_{3}$ceramics was synthesized. The relative density was successfully increased. Concerning the electrical properties, the relative permittivity was improved, and the piezoelectric constant d$_{33}$ was also increased from 114 to 130 pC/N. AU - Maeda, Takafumi AU - Hemsel, Tobias AU - Morita, Takeshi ID - 9769 JF - Japanese Journal of Applied Physics TI - Improved Process for Hydrothermal Lead-Free Piezoelectric Powders and Performances of Sintered (K0.48Na0.52)NbO3 Ceramics VL - 50 ER - TY - JOUR AU - Isobe, Gaku AU - Bornmann, Peter AU - Hemsel, Tobias AU - Morita, Takeshi ID - 9877 JF - Proceedings of Symposium on Ultrasonic Electronics TI - High temperature tolerant transducer for Ultrasonic Assisted Hydrothermal Method VL - 32 ER - TY - GEN AB - Es wird eine Anordnung zur mehrdimensionalen Messung von Schwingungen eines Objektes vorgeschlagen, umfassend ein Vibrometer und eine erste Ablenkeinheit, mittels welcher der Messstrahl des Vibrometers in wenigstens zwei erste Raumrichtungen ablenkbar ist, sowie wenigstens eine zweite Ablenkeinheit, mittels welcher der aus einer der wenigstens zwei ersten Raumrichtungen auf eine zweite Ablenkeinheit eintreffende Messstrahl derart ablenkbar ist, dass ein Messpunkt des Objekts aus einer ersten Raumrichtung und wenigstens einer zweiten Raumrichtung oder wenigstens zwei zweiten Raumrichtungen damit erfassbar ist. Bei dem zum Betrieb der Anordnung vorgesehenen Verfahren wird der Messstrahl eines Vibrometers in wenigstens zwei erste Raumrichtungen abgelenkt, woraufhin wenigstens ein Messstrahl einer ersten Raumrichtung ein zweites Mal derart abgelenkt wird, dass ein Messpunkt des Objekts aus einer ersten Raumrichtung und wenigstens einer zweiten Raumrichtung oder wenigstens zwei zweiten Raumrichtungen erfasst wird, insbesondere so dass die zu untersuchenden Bewegungskomponenten in den Messsignalen, welche entlang der ersten und zweiten Raumrichtungen gewonnen werden, enthalten sind. The arrangement has a first deflecting unit (3) for deflecting a measuring beam of a vibrometer (2) in spatial directions (4-6, 4-6). Second and third deflecting units (7, 8) deflect the beam arriving from one of the spatial directions such that a measuring point (9) of an object (1) is detectable with the beam from the spatial direction or the spatial directions. The first deflecting unit is designed as a scanning unit, where the measuring point is detected by the scanning unit. A measuring instrument measures focus quality and is connected to actuators for adjustment of the focus quality. An independent claim is also included for a method for multidimensional measurement of oscillations of an object. AU - Sextro, Walter AU - Hunstig, Matthias AU - Bornmann, Peter AU - Hemsel, Tobias ID - 9790 TI - Patent DE10201003395: Anordnung und Verfahren zur mehrdimensionalen Messung von Schwingungen eines Objekts. ER - TY - JOUR AB - The hydrothermal method enables the production of high-quality piezoelectric materials. In this study, we propose to irradiate the reaction solutions with ultrasonic power during the hydrothermal method to obtain a shorter reaction time and a smooth film surface. A high-pressure reaction container for the ultrasonic transducer was newly developed, and the ultrasonically-assisted hydrothermal method was examined by using this container. The effect of ultrasonic assist on the synthesis of lead-zirconate-titanate (PZT) thin films and (K,Na)NbO$_{3}$ powders was verified. Thicker PZT film, thickness around 10 ${\mu}$m, could be obtained in one process, and (K,Na)NbO$_{3}$ powder was synthesized in half the previous reaction time. AU - Ageba, Ryo AU - Kadota, Yoichi AU - Maeda, Takafumi AU - Takiguchi, Norihito AU - Morita, Takeshi AU - Ishikawa, Mutsuo AU - Bornmann, Peter AU - Hemsel, Tobias ID - 9743 IS - 4 JF - Journal of Korean Physical Society KW - Hydrothermal method KW - High-power ultrasonic KW - PZT thin film KW - Lead-free piezoelectric materials SN - 1948-5719 TI - Ultrasonically-assisted Hydrothermal Method for Ferroelectric Material Synthesis VL - 57 ER - TY - JOUR AB - Direct ultrasound irradiation is advantageous to increase the efficiency of the hydrothermal method which can be used for the production of piezoelectric thin films and lead free piezoelectric ceramics. To apply ultrasound directly to the process transducer prototypes were developed regarding the boundary conditions of the hydrothermal method. LiNbO$_{3}$ and PIC 181 were proven as feasible materials for high temperature resistant transducers ($\geq 200^\circ C$). Resistance of the transducers horn against the corrosive mineralizer was achieved by using Hastelloy C-22. The efficiency of the ultrasound assisted hydrothermal method depends on the generated sound field. Impedance and sound field measurements have shown that the sound field depends on the filling level and the position and design of the transducer. AU - Bornmann, Peter AU - Hemsel, Tobias AU - Littmann, Walter AU - Ageba, Ryo AU - Kadota, Yoishi AU - Morita, Takeshi ID - 9744 IS - 4 JF - Journal of Korean Physical Society KW - High-temperature transducer KW - Hydrothermal method KW - Lithium-niobate transducer SN - 1948-5719 TI - Ultrasonic Transducer for the Hydrothermal Method VL - 57 ER - TY - JOUR AB - In the modeling of piezoelectric Langevin transducers using usual transfer matrix methods, some simplifications have been adopted. This leads to reduction of the model quality. A mixed transfer matrix method is employed in the modeling of Langevin transducers, where the pre-stressed bolt is modeled as a separate four-pole element, which is connected to other elements in parallel. Based on the mixed transfer matrix method, the four (six)-pole element description of the piezoelectric Langevin transducer is built up and the total transfer matrix relation is derived. The resonance frequencies of the transducer are calculated and then measured using the impedance analyzer (HP4192). Experimental result shows that the mixed transfer matrix method has better modeling quality than the usual transfer matrix method for the vibration analysis of piezoelectric Langevin transducers. AU - Fu, Bo AU - Li, Chao AU - Zhang, Jianming AU - Huang, Zhenwei AU - Hemsel, Tobias ID - 9745 IS - 4 JF - Journal of Korean Physical Society KW - Piezoelectric langevin transducer KW - Transfer matrix method KW - Four (six)-pole element description KW - Pre-stressed bolt SN - 1948-5719 TI - Modeling of Piezoelectric Langevin Transducers by Using Mixed Transfer Matrix Methods VL - 57 ER - TY - JOUR AB - Piezoelectric materials find wide application in technical systems. Most often, a combination of piezoelectric and other materials is advantageous. The position and the amount of the piezoelectric material within the overall system depends on various aspects like maximum mechanical output to the load, maximum electromechanical efficiency of the system, maximum utilization of the piezoelectric material, minimum self-heating of the piezoelectric material, and controllability of the system, which might be key aspects for the optimisation of the system design. For a composite longitudinal vibrator (bolted Langevin transducer), which is a base for many technical applications, this contribution shows in detail, how above mentioned aspects depend on the position and volume of the piezoelectric material related to the mode shape. AU - Hemsel, Tobias AU - Lierk, Ernst Günther AU - Littmann, Walter AU - Morita, Takeshi ID - 9749 IS - 4 JF - Journal of Korean Physical Society KW - Bolted Langevin transducer KW - Optimum placement of piezoelectric ceramics SN - 1948-5719 TI - Various Aspects of the Placement of a Piezoelectric Material in Composite Actuators, Motors, and Transducers VL - 57 ER - TY - JOUR AB - Piezoelectric inertia motors have a simple construction and are controlled by a single driving signal. This allows for miniaturization and low cost production. One of the main questions to be answered during the design process of a piezoelectric inertia motor is which electrical excitation signal yields optimum motor characteristics. Three signals and their variants are widely used in literature: sawtooth, parabolic and cycloidic signals. It can be shown that neither of these can drive the motor at its maximum possible velocity in non-resonant operation. Within this paper we propose to use a rigid body model of a simple inertia motor to predict the motor characteristics depending on the movement pattern of the driving element. Advantages and disadvantages of three different drive signals that maximize the motor velocity are discussed. AU - Hunstig, Matthias AU - Hemsel, Tobias ID - 9751 IS - 4 JF - Journal of Korean Physical Society SN - 1948-5719 TI - Drive Signals for Maximizing the Velocity of Piezoelectric Inertia Motors VL - 57 ER - TY - JOUR AB - Piezoelectric inertia motors make use of the inertia of a slider to drive the slider by friction contact in a series of small steps which are generally composed of a stick phase and a slip phase. If the best electrical drive signal for the piezoelectric actuator in an inertia motor is to be determined, its dynamical behaviour must be known. A classic dynamic lumped parameter model for piezoelectric actuators is valid only in resonance and, therefore, is not suitable for modelling the actuator in an inertia motor. A reduced dynamic model is used instead. Its parameters are identified using a step response measurement. This model is used to predict the movement of the actuator in response to a velocity-optimized signal introduced in a separate contribution. Results show that the model cannot represent the dynamical characteristics of the actuator completely. For determining voltage signals that let piezoelectric actuators follow a calculated movement pattern exactly, the model can, therefore, only be used with limitations. AU - Hunstig, Matthias AU - Hemsel, Tobias ID - 9752 IS - 4 JF - Journal of Korean Physical Society SN - 1948-5719 TI - Parameter Identification and Model Validation for the Piezoelectric Actuator in an Inertia Motor VL - 57 ER - TY - CONF AB - Piezoelektrische Trägheitsmotoren nutzen die Trägheit einer bewegten Masse, um diese in kleinen Schritten durch abwechselnde Haft- und Gleitphasen voranzutreiben. Eine Kernfrage bei der Entwicklung eines piezoelektrischen Trägheitsmotors ist, welches elektrische Ansteuersignal für das gewünschte Motorverhalten optimal ist. Das elektrische Signal führt zu einer Bewegung des piezoelektrischen Aktors und damit der Antriebsstange, die den reibschlüssigen Vortrieb bewirkt. Entsprechend wird diese Fragestellung in zwei Teilen untersucht: Anhand eines Starrkörpermodells werden zunächst Bewegungsverläufe für die Antriebsstange ermittelt, mit denen die maximale Geschwindigkeit erreicht wird. Dabei werden drei Antriebsmodi identifiziert. Mit allen kann eine höhere Geschwindigkeit als mit der heute häufig verwendeten Sägezahnanregung erreicht werden. Anschließend wird ein einfaches dynamisches Modell eines piezoelektrischen Aktors genutzt, um die notwendigen elektrischen Ansteuersignale für die verschiedenen Antriebsmodi zu bestimmen. Es zeigt sich, dass das gewählte einfache Modell hierzu nur bedingt geeignet ist. AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ED - Gausemeier, Jürgen ED - Rammig, Franz ED - Schäfer, Wilhelm ED - Trächtler, Ansgar ID - 9753 KW - Piezoelektrischer Trägheitsmotoren SN - 0924-4247 T2 - 7. Paderborner Workshop Entwurf mechatronischer Systeme TI - Anregungskonzepte und Modellierung piezoelektrischer Trägheitsmotoren VL - 272 ER - TY - CONF AB - A model based design approach for improved piezoelectric inertia motors is presented. Three velocityoptimized movement patterns for the driving body have been derived. The influence of the motor parameters and the process of designing an application specific motor with maximum velocity are shown. A simple dynamic model of the piezoelectric actuator is used to calculate the voltage signal for achieving the desired movement pattern. Observed distortions of the optimum pattern, their influence on the motion of the driven body and different methods to reduce them are discussed. AU - Hunstig, Matthias AU - Hemsel, Tobias AU - Sextro, Walter ID - 9754 SN - 0924-4247 T2 - ACTUATOR 2010 Conference Proceedings TI - Improving the Performance of Piezoelectric Inertia Motors ER - TY - CONF AU - Kraft , Verena AU - Bauch, C. AU - Nückel, M. AU - Hemsel, Tobias ID - 9755 T2 - 19. Gemeinschaftstagung LICHT 2010 TI - Konzeption und Aufbau eines Langzeitforschungsstandes zur lichttechnischen Charakterisierung von organischen Leuchtdioden (OLEDs) ER - TY - JOUR AB - Dieser Beitrag fasst die bekannten analytischen Berechnungsmethoden für piezoelektrische Ultraschallverbundschwinger zusammen und gibt anhand typischer Beispiele Anleitungen zur Lösung theoretischer und technischer Fragen bei deren Entwicklung. Zunächst werden die passiven, in der Regel metallischen Komponenten von Verbundschwingern als Stab- oder Plattensysteme mit homogen verteilten Feder-, Masse und Dämpfungseigenschaften beschrieben. Hier breitet sich die Schwingungsenergie in Form stehender und fortschreitender Wellen zum akustischen Verbraucher hin aus. Es folgt eine gleichwertige und schaltungstreue Darstellung durch elektrische oder mechanische Vierpole, die für den Entwicklungsingenieur leichter zu handhaben sind und in Netzwerken direkt mit Masons Ersatzschaltung des piezoelektrischen Wandlers gekoppelt werden können. Danach werden die wichtigsten, messtechnisch zugänglichen Parameter anhand eines in Resonanznähe zulässigen Ersatzmodells mit konzentrierten elektrischen bzw. mechanischen Komponenten definiert. Als Schwerpunkt wird anschließend deren analytische Berechnung und messtechnische Verifizierung an typischen Beispielen demonstriert. Es folgen wichtige technische Informationen über Frequenzkorrekturen, Schallgeschwindigkeitsdispersion, Leistungs- und Belastbarkeitsgrenzen der Komponenten und andere wertvolle praktische Hinweise. AU - Lierke, Ernst-Günter AU - Littmann, Walter AU - Hemsel, Tobias ID - 9756 JF - Veröffentlichung der Universität Paderborn SN - 1948-5719 TI - Zur Theorie der piezoelektrischen Ultraschallverbundschwinger mit praktischen Schlussfolgerungen für den Entwicklungsingenieur ER - TY - JOUR AU - Lucinskis, Raimundas AU - Mazeika, Dalius AU - Hemsel, Tobias AU - Bansevicius, Ramutis ID - 9757 JF - MECHANIKA SN - 1948-5719 TI - The experimental research of piezoelectric actuator with two vectors of polarization direction ER - TY - JOUR AB - As a lead-free piezoelectric ceramics, (K,Na)NbO$_{3}$ is a promising material because of its good piezoelectric properties. In this study, (K$_{1-x}$Na$_{x}$)NbO$_{3}$ ceramics were synthesized from a KNbO$_{3}$ and NaNbO$_{3}$ mixture powder prepared by the hydrothermal reaction. The hydrothermal reaction enables the production of high quality powder for the ceramics fabrication process. To obtain (K$_{1-x}$Na$_{x}$)NbO$_{3}$ ceramics, these two powders KNbO$_{3}$ and NaNbO$_{3}$ were mixed and then sintered together. X-Ray diffraction analysis revealed that the solid solution ceramics (K$_{1-x}$Na$_{x}$)NbO$_{3}$ was produced by the sintering process. The K/Na ratio in (K$_{1-x}$Na$_{x}$)NbO$_{3}$ ceramics was optimized for the best piezoelectric properties. The optimized forms was (K$_{0.48}$Na$_{0.52}$)NbO$_{3}$, which showed the following piezoelectric properties; k$_{33}$=0.56, d$_{33}$=114pC/N. In addition, the ferroelectric properties, P$_{r}$=7.72mC/cm$^{2}$, E$_{c}$=857V/mm, and the Curie temperature T$_{c}$=420$_{o}$C were also measured. AU - Maeda, Takafumi AU - Takiguchi, Norihito AU - Morita, Takeshi AU - Ishikawa, Mutsuo AU - Hemsel, Tobias ID - 9758 IS - 4 JF - Journal of Korean Physical Society KW - Lead-free piezoelectric material KW - KNN KW - Hydrothermal method SN - 1948-5719 TI - Hydrothermal (K1-xNax)NbO3 Lead-free Piezoelectric Ceramics VL - 57 ER - TY - JOUR AB - Among various lead-free piezoelectric materials, (K,Na)NbO$_{3}$ is a very promising candidate. In this study, (K,Na)NbO$_{3}$ ceramics were sintered from mixed (K,Na)NbO$_{3}$ and NaNbO$_{3}$ powders prepared by hydrothermal reaction. These two powders were mixed with distilled water in a KNbO$_{3}$/NaNbO$_{3}$ molar ratio of 1. After sintering the mixed powder, the solid solution of (Na,K)NbO$_{3}$ ceramics was obtained. The electrical properties such as the electromechanical coupling factors k$_{p}$ and k$_{33}$, the mechanical quality factor, Q$_{m}$, and the piezoelectric constant d$_{33}$ of the sintered (K,Na)NbO$_{3}$ ceramics were 0.32, 0.48, 71 (radial mode), 118 ((33)mode), and 107 pC/N, respectively. AU - Maeda, Takafumi AU - Takiguchi, Norihito AU - Morita, Takeshi AU - Ishikawa, Mutsuo AU - Hemsel, Tobias ID - 9759 IS - 2 JF - Materials Letters KW - Lead-free piezoelectric material KW - (K KW - Na)NbO$_{3}$ ceramics KW - Sintering solid solution KW - Piezoelectric properties SN - 1948-5719 TI - (K,Na)NbO3 lead-free piezoelectric ceramics synthesized from hydrothermal powders VL - 64 ER - TY - CONF AB - Self-optimizing systems are able to adapt their behavior autonomously according to their current self-determined objectives. Unforeseen influences could lead to dependability-critical behavior of the system. Methods are required which secure self-optimizing systems during operation. These methods to increase the dependability of the system should already be taken into consideration in the design process. This paper presents a guideline for the dependability-oriented design of self-optimizing systems, which integrates established classical methods like failure mode and effects analysis as well as methods based on self-optimization. On the one hand self-optimization is used to increase the dependability of the system by integrating objectives like safety, availability, and reliability to the objectives of the system. On the other hand methods are required to ensure the self-optimization itself. As basis for this guideline serves the principle solution of the system. The six phases of the guideline extend the design process and lead to an enhanced principle solution. Additionally, the guideline illustrates phases to implement and validate the self-optimizing system. The proposed guideline is applied to an innovative rail-bound vehicle, called RailCab, which is equipped with self-optimizing function modules. AU - Sondermann-Wölke, Christoph AU - Hemsel, Tobias AU - Sextro, Walter AU - Gausemeier, Jürgen AU - Pook, Sebastian ID - 9760 KW - RailCab KW - dependability-critical behavior KW - dependability-oriented design KW - failure mode KW - rail-bound vehicle KW - secure self-optimizing systems KW - self-optimizing function modules KW - optimisation KW - railways KW - self-adjusting systems T2 - Industrial Informatics (INDIN), 2010 8th IEEE International Conference on TI - Guideline for the dependability-oriented design of self-optimizing systems ER - TY - JOUR AU - Sondermann-Wölke, Christoph AU - Geisler, Jens AU - Hirsch, Martin AU - Hemsel, Tobias ID - 23230 JF - 6. Paderborner Workshop: "Entwurf mechatronischer Systeme" TI - Verlässlichkeit im aktiven selbstoptimierenden Spurführungsmodul eines schienengebundenen Fahrzeugs VL - Band 250 ER - TY - JOUR AU - Sondermann-Wölke, Christoph AU - Geisler, Jens AU - Hirsch, Martin AU - Hemsel, Tobias ID - 23249 JF - 6. Paderborner Workshop: "Entwurf mechatronischer Systeme" TI - Verlässlichkeit im aktiven selbstoptimierenden Spurführungsmodul eines schienengebundenen Fahrzeugs VL - Band 250 ER - TY - CONF AB - Die Entwicklung piezoelektrischer Tr{\"a}gheitsmotoren basiert derzeit auf Erfahrungswissen und Prototypenbau. Es existiert kein allgemeines Modell und keine Methodik f{\"u}r die systematische Entwicklung dieser Motoren. In diesem Beitrag stellen wir einen Ansatz zur Entwicklung einer solchen Methodik und den von uns aufgebauten Versuchsmotor vor. Der Motor ist modular aufgebaut; er besteht im Wesentlichen aus einer piezoelektrischen Antriebseinheit, einem Antriebsstab und dem zu bewegenden Schlitten. Eine wesentliche Aufgabe bei der modellbasierten Entwicklung von Tr{\"a}gheitsmotoren ist die hinreichende Beschreibung des dynamischen Verhaltens der Antriebseinheit. Um ein geeignetes Modell zu finden, bzw. um nachzuweisen, dass einfache parametrische Modelle gen{\"u}gen, wird die Antriebseinheit des Motors detailliert untersucht. Es zeigt sich, dass der derzeitige Aufbau eine Reihe von Nachteilen aufweist, die durch eine teilweise Neukonstruktion der Antriebseinheit beseitigt oder zumindest entsch{\"a}rft werden k{\"o}nnen. AU - Hunstig, Matthias AU - Hemsel, Tobias ED - Gausemeier, Jürgen ED - Rammig, Franz ED - Schäfer, Wilhelm ED - Trächtler, Ansgar ID - 9735 KW - Piezoelektrischer Tr{\ SN - 1948-5719 T2 - 6. Paderborner Workshop Entwurf mechatronischer Systeme TI - Modellbasierte Entwicklung piezoelektrischer Trägheitsmotoren VL - 250 ER - TY - CONF AB - Die Integration von Selbstoptimierung in mechatronische Systeme beinhaltet sowohl Risiken als auch Potenziale für die Verlässlichkeit. Die Risiken entstehen durch die Selbstoptimierung in den komplexen Systemen, da das Systemverhalten nur begrenzt im Voraus vorhersehbar ist. Daher wurde innerhalb des Sonderforschungsbereichs 614 ''Selbstoptimierende Systeme des Maschinenbaus" ein mehrstufiges Verlässlichkeitskonzept entworfen, welches das Ziel Verlässlichkeit stärker im Zielsystem verankert. In diesem Beitrag wird zum einen das erarbeitete Verlässlichkeitskonzept und zum anderen die Anwendung dieses Konzepts innerhalb des aktiven Spurführungsmoduls eines schienengebundenen Fahrzeugs vorgestellt. Um Programmierfehler auszuschließen wurde das Verlässlichkeitskonzept modelliert und über Model Checking verifiziert. Anhand von Simulationsergebnissen wird gezeigt, wie durch das mehrstufige Verlässlichkeitskonzept auf einen Ausfall eines Wirbelstromsensors des aktiven Spurführungsmoduls reagiert werden kann. AU - Sondermann-Wölke, Christoph AU - Geisler, Jens AU - Hirsch, Martin AU - Hemsel, Tobias ED - Gausemeier, Jürgen ED - Rammig, Franz Josef ED - Trächtler, Ansger ID - 9740 KW - Verlässigkeit T2 - Entwurf mechatronischer Systeme TI - Verlässlichkeit im aktiven selbstoptimierenden Spurführungsmodul eines schienengebundenen Fahrzeugs VL - 250 ER - TY - CONF AU - Sondermann-Wölke, Christoph AU - Hesse, Tobias AU - Sattel, Thomas AU - Hemsel, Tobias ID - 9741 T2 - 24. Tagung Technische Zuverlässigkeit (TTZ 2009) - Entwicklung und Betrieb zuverlässiger Produkte, Leonberg TI - Menschliche Unzuverlässigkeit als Grundlage für den Entwurf von Kollisionsvermeidungssystemen. VL - 2065 ER - TY - CONF AB - A simple pre-stress estimate method of Langevin transducers is studied. The measurement setup consists of a capacitor, an impedance converter and a voltmeter. Based on the piezoelectric equation and the basic circuit theory, the mathematical expression between the pre-stress and the voltage across the capacitor is derived. The pre-stress level can then be calculated out of the measurement of the capacitor voltage. In order to evaluate the precision of this method, a force washer is used to measure the pre-stress of the Langevin transducer. The result shows the pre-stress level obtained from this method is 30-40\% higher than the pre-stress level measured by the force washer. This method is simple and can be used to estimate the pre-stress of various Langevin transducers. The precision of this method can be raised if d33 is identified under different pre-stress levels. AU - Bo, Fu AU - Ting, Li AU - Hemsel, Tobias ID - 9568 KW - capacitors KW - impedance convertors KW - piezoelectric transducers KW - stress analysis KW - Langevin transducers KW - basic circuit theory KW - capacitor KW - impedance converter KW - piezoelectric equation KW - pre-stress estimating method KW - voltmeter KW - Capacitors KW - Educational institutions KW - Equations KW - Force measurement KW - Impedance measurement KW - Manufacturing KW - Mechatronics KW - Piezoelectric transducers KW - Voltage KW - Voltmeters KW - Langevin transducer KW - capacitor KW - piezoelectric element KW - pre-stress T2 - Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium on TI - A simple pre-stress estimating method of langevin transducers ER - TY - JOUR AB - Ultrasonic hyperthermia and thermo-ablation are two promising alternatives for local overheating of deep-seated human tumours. After a short characterisation of the two techniques and the identification of the main parameters, results of an analytical theory of local heat up, cooling, and heat diffusion are presented. The theory is based on a spherical model for hyperthermia with a critical thermal dose and on a cylinder-symmetrical model for thermo-ablation with a critical temperature threshold for thermal toxicity and cell death through coagulative necrosis. Two representative hard ware concepts are discussed. The hyperthermia applicator consists of a MHz transducer, which rotates concentrically in a water filled capsule with acoustically transparent window, and radiates collimated or focussed ultrasound under 45$\,^{\circ}$ into a concentric target area of nearly spherical symmetry. The applicator for thermo-ablation is a MHz transducer which radiates high intensity focussed ultrasound (HIFU) into "cigar shaped" target areas at the focal zone. Typical therapy diagrams for both techniques are presented. They show therapeutic target volumes as functions of the therapy time with the peak temperature or the radiated acoustic power as parameters. These diagrams are discussed under consideration of power requirement, maximal sound intensity, and power efficiency at close to optimized frequency conditions. AU - Lierke, Ernst-Günter AU - Hemsel, Tobias ID - 9569 IS - 3 JF - Acta Acustica united with Acustica TI - Local Ultrasonic Hyperthermia and Thermo-ablation: A Description and Theoretical Evaluation of Two Alternative Concepts for the Heat Therapy of Tumours VL - 94 ER - TY - CONF AB - EN: Although the use of new actuator technologies is quite enthusiastic, the realization of innovative systems based on these principles fails because of doubts in dependability. Until now, new working principles for actuators have not been systematically investigated in the means of dependability. Therefore we developed a proceeding for a dependability-oriented evaluation of technologies. This is shown in the case of shape memory alloy actuators. DE: Die Realisierung von Systemen mittels innovativer Aktortechnologien scheitert oftmals an der Skepsis gegenüber der Verlässlichkeit (Vertrauen in die zuverlässige und sichere Funktionalität der Technologie). Diese liegt darin begründet, dass neue Aktortechnologien bzw. die Integration von innovativen physikalischen Wirkprinzipen innerhalb neuer Aktorkonzepte bisher noch nicht systematisch im Kontext der Verlässlichkeit untersucht werden. Daher haben wir ein Vorgehen zur verlässlichkeitsorientierten Technologiebewertung entwickelt. Neben der detaillierten Darstellung des Vorgehensmodells wird es exemplarisch anhand von Formgedächtnislegierungen zur Entwicklung innovativer Antriebslösungen angewendet. AU - Müller, Thomas AU - Schiedeck, Florian AU - Hemsel, Tobias ID - 9570 KW - EN: Dependability KW - Reliability KW - Evaluation of Technology KW - Actuators KW - Shape Memory Alloys DE: Verl{\ T2 - 2. Tagung des DVM -- Arbeitskreis Zuverlässigkeit mechatronischer und adaptronischer Systeme: Absicherung der Systemzuverlässigkeit, Koblenz TI - Verlässlichkeitorientierte Technologiebewertung innovativer Aktortechnologien am Beispiel von Formgedächtnislegierungen ER - TY - JOUR AB - Several positioning tasks demand translatory drive instead of rotary motion. To achieve drives that are capable, e.g., to drive the sunroof of a car or to lift a car's window, multiple miniaturized motors can be combined. But in this case many other questions arise: The electromechanical behavior of the individual motors differs slightly, the motor characteristics are strongly dependent on the driving parameters and the driven load, many applications need some extra power for special cases like overcoming higher forces periodically. Thus, the bundle of motors has to act well-organized and at last controlled to get an optimized drive that is not oversized and costly. AU - Mracek, Maik AU - Hemsel, Tobias AU - Sattel, Thomas AU - Vasiljev, Piotr AU - Wallaschek, Jörg ID - 9571 IS - 3-4 JF - Journal of Electroceramics KW - Ultrasonic linear motor KW - High power KW - Control KW - Modeling KW - Characteristics SN - 1385-3449 TI - Driving concepts for bundled ultrasonic linear motors VL - 20 ER - TY - JOUR AB - For devices having non-linear contact, load plays a fundamental role. Variations in the characteristics of the load cause change in eigenfrequency and amplitude of the vibration. In most technical applications, this unwanted behaviour is cancelled by the use of control algorithms. However, multiple applications, like bond quality monitoring or chemical and pressure sensors, have found that the load may be characterised by interpreting the change in characteristics of a resonant vibrating device used as a sensor. Surgical resection of tumours is a very difficult task. After localising the tumour by the use of imaging techniques, the resection demands the surgeon to decide where and what to resect based on visual and tactile differentiation of tumour and healthy tissue. Exactness of this process could be enhanced if we can provide the surgeon with a device capable of evaluating mechanical characteristics of the tissue much more accurately than the surgeon himself can do. As the mechanical characteristics of tumour and healthy tissue differ but slightly, the task is to design a system with high sensitivity. Therefore, we have developed a resonant actuator-sensor that allows the differentiation among distinct media that have similar mechanical characteristics to tumour and healthy tissue using a piezoelectric bimorph. The design is based on the detection and evaluation of frequency shift and amplitude variation of the fundamental and higher harmonics using one layer for the resonant excitation of vibration and the other one as the sensing element. AU - Stroop, Ralf AU - Uribe, David Oliva AU - Martinez, Melisa Orta AU - Brökelmann, Michael AU - Hemsel, Tobias AU - Wallaschek, Jörg ID - 9574 IS - 3-4 JF - Journal of Electroceramics KW - Piezo ceramics KW - Bimorph KW - Tactile sensor KW - Tumour tissue SN - 1385-3449 TI - Tactile tissue characterisation by piezoelectric systems VL - 20 ER - TY - JOUR AB - Many ultrasonic processes are based on the mechanical contact of oscillating parts. Within ultrasonic machining (drilling, milling, grinding) micro impacts lead to abrasion at the processed workpiece and hopefully do not damage the tool. In ultrasonic motors ideally neither part gets worn. Thus the appropriate design of contact partners as well as their kinematics is a substantial task during the development of such devices. A first step to optimize contact mechanics is to understand their behavior and dependencies on parameter variations, such as vibration amplitude and pre-stress of the impacting parts. For a detailed understanding models validated with convincing experimental data from measurements are absolutely essential. This paper focuses on simple vibro-impact experiments which can be used as benchmark data for future models. The setup of the experiment and first experimental investigations are described in detail. AU - Twiefel, Jens AU - Potthast, Christian AU - Mracek, Maik AU - Hemsel, Tobias AU - Sattel, Thomas AU - Wallaschek, Jörg ID - 9575 IS - 3-4 JF - Journal of Electroceramics KW - Contact measurements KW - Vibro-impact KW - Ultrasonic application SN - 1385-3449 TI - Fundamental experiments as benchmark problems for modeling ultrasonic micro-impact processes VL - 20 ER - TY - CONF AB - In neurosurgery, delineation of tumor boundaries during resection of brain tumors is of substantial relevance. During operation distinction between tumor and healthy tissue rely on the abilities of the surgeon based on visual and tactile differentiation. In this paper a high sensitivity actuator-sensor system using a piezoelectric bimorph is presented. Frequency shift and transfer function of the bimorphpsilas voltages are detected and evaluated. Sensorpsilas sensitivity is evaluated using two frequency controls strategies: A phase-locked loop (PLL) and a self-oscillating circuit. Results of measurements conducted on gel-phantoms are presented and discussed. AU - Uribe, David Oliva AU - Stroop, Ralf AU - Hemsel, Tobias AU - Wallaschek, Jörg ID - 9576 KW - biomedical measurement KW - brain KW - cancer KW - neurophysiology KW - phantoms KW - phase locked loops KW - piezoelectric actuators KW - surgery KW - tactile sensors KW - transfer functions KW - tumours KW - PLL KW - biomedical tissue differentiation system KW - brain tumor resection KW - frequency control KW - frequency shift KW - gel-phantom KW - high sensitivity actuator-sensor system KW - neurosurgery KW - phase-locked loop KW - piezoelectric actuators KW - piezoelectric bimorph KW - self-oscillating circuit KW - sensor sensitivity KW - tactile differentiation KW - tactile sensor system KW - transfer function KW - tumor boundary KW - visual differentiation KW - Biomedical measurements KW - Circuits KW - Frequency control KW - Neoplasms KW - Neurosurgery KW - Phase locked loops KW - Piezoelectric actuators KW - Surges KW - Transfer functions KW - Voltage SN - 1075-6787 T2 - Frequency Control Symposium, 2008 IEEE International TI - Development of a biomedical tissue differentiation system using piezoelectric actuators ER - TY - GEN AU - Rischmueller, Volker AU - Wallaschek, Jörg AU - Froehlich, Peter AU - Haussecker, Walter AU - Rieger, Vincent AU - Twiefel, Jens AU - Guenther, Dirk AU - Hemsel, Tobias ID - 9572 TI - Patent EP2156480: Piezoelektrische Antriebsvorrichtung / Piezoelectric Drive Unit ER - TY - CONF AB - Penetration tests (Magness-Taylor, force/deformation, Kramer multiblade shear) applied directly over the peel of the fruit are the most acceptable methods for measuring firmness and turgidity of fruits and vegetables [1, 2]. To replace these destructive and mechanical penetration methods by non-destructive ultrasonic measurements implies a great advance in order to obtain fast studies about the state of the fruit at the time of harvest, during storage, and in the distribution points. Moreover, there are other advantages since this technique can be fast, non-destructive, fully automated, and performed on-line [1]. Within this context, the objective of this study was to examine the relationship between physico-mechanical characteristics (oil-gland break stress, thickness and dehydration) and ultrasonic characteristics in the ``Salustiana'' orange peel during the complete dehydration process of the orange at ambient conditions. After a description of the measurement system [3], the fruit selection procedure and the measurement protocol, we analyze the results of the change of physico-mechanical and ultrasonic properties in the orange peel and their change with storage time. AU - Camarena Gandia, Francisco AU - Hemsel, Tobias AU - Espinosa, Victor AU - Twiefel, Jens AU - Ardid, Miquel AU - Martinez-Mora, Joan AU - Gandia, Joan Babtiste ID - 9562 T2 - Proceedings of 19th international congress on Acoustics, Madrid TI - Non-destructive ultrasonic test of orange dehydration ER - TY - JOUR AB - Surgical resection of brain tumours is a difficult task. To enhance surgery results, a tactile sensor is wanted that gives better resolution and sensitivity than the human tactile sense. The characteristics of resonant vibrating piezoelectric elements change with varying load. This allows for calculation of mechanical load parameters by measuring electrical quantities. Different setups of piezoelectric sensors have been used to investigate soft materials. Finally, a piezoelectric bimorph sensor gave good results for distinguishing tissue mimicking gel-phantoms with different gelatine concentrations. AU - Hemsel, Tobias AU - Stroop, Ralf AU - Oliva Uribe, David AU - Wallaschek, Jörg ID - 9564 JF - Journal of Sound and Vibration SN - 0022-460X TI - Resonant vibrating sensors for tactile tissue differentiation VL - 308 ER - TY - CONF AU - Lierke, Ernst-Günter AU - Hemsel, Tobias ID - 9565 T2 - Proceedings of 19th international congress on Acoustics, Madrid TI - Perspectives of Tumour Therapy by Local Ultrasonic Hyperthermia and Thermal Ablation ER - TY - JOUR AU - Shigematsu , Takashi AU - Morita, Takeshi AU - Hemsel, Tobias ID - 9566 JF - Proceedings of Symposium on Ultrasonic Electronics TI - Fundamental Study on A Thickness-Shear Transformer using X-Cut Lithium Niobate VL - 28 ER - TY - CONF AU - Becker, C AU - Wedman, S AU - Hemsel, Tobias ID - 9532 IS - Band 180 T2 - Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators TI - Design and Construction of a 3D-Scanning-Laservibrometer ER - TY - JOUR AB - The design of piezoelectric transducers is usually based on single-objective optimization only. In most practical applications of piezoelectric transducers, however, there exist multiple design objectives that often are contradictory to each other by their very nature. It is impossible to find a solution at which each objective function gets its optimal value simultaneously. Our design approach is to first find a set of Pareto-optimal solutions, which can be considered to be best compromises among multiple design objectives. Among these Pareto-optimal solutions, the designer can then select the one solution which he considers to be the best one. In this paper we investigate the optimal design of a Langevin transducer. The design problem is formulated mathematically as a constrained multiobjective optimization problem. The maximum vibration amplitude and the minimum electrical input power are considered as optimization objectives. Design variables involve continuous variables (dimensions of the transducer) and discrete variables (the number of piezoelectric rings and material types). In order to formulate the optimization problem, the behavior of piezoelectric transducers is modeled using the transfer matrix method based on analytical models. Multiobjective evolutionary algorithms are applied in the optimization process and a set of Pareto-optimal designs is calculated. The optimized results are analyzed and the preferred design is determined. AU - Fu, Bo AU - Hemsel, Tobias AU - Wallaschek, Jörg ID - 9533 JF - Ultrasonics KW - Piezoelectric transducer SN - 0041-624X TI - Piezoelectric transducer design via multiobjective optimization VL - 44, Supplement ER - TY - CONF AU - Fu, Bo AU - Hemsel, Tobias AU - Wallaschek, Jörg ID - 9534 IS - Band 180 T2 - Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators TI - Multiobjective optimization of piezoelectric transducers using evolutionary algorithms ER - TY - CONF AU - Hemsel, Tobias AU - Henning, C AU - Kauczor, Christopher AU - Littmann, Walter ID - 9537 IS - Band 180 T2 - Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators TI - Powder coating fabrication by ultrasonic standing wave atomizer ER - TY - CONF AU - Hemsel, Tobias AU - Mracek, Maik ID - 9538 IS - Band 180 T2 - Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators TI - Control of Bundled Miniature Ultrasonic Linear Motors ER - TY - JOUR AB - Classically, rotary motors with gears and spindle mechanisms are used to achieve translatory motion. In means of miniaturization and weight reduction piezoelectric linear motors are of interest. Several ultrasonic linear motors found in literature base on the use of two different vibration modes. Most often flexural and longitudinal modes are combined to achieve an elliptic micro-motion of surface points. This micro-motion is converted to direct linear (or translatory) motion of a driven slider. To gain high amplitudes of the micro-motion and thus having a powerful motor, the ultrasonic vibrator should be driven near the eigenfrequency of its modes. Additionally, low mechanical and electrical losses lead to increased efficiency and large amplitude magnification in resonance. This demands a geometrical design that fits the eigenfrequencies of the two different modes. A frequency-deviation of only a few percent leads to non-acceptable disturbance of the elliptical motion. Thus, the mechanical design of the vibrators has to be done very carefully. Within this contribution we discuss different motor designs based on the coupling of two the same longitudinal vibrations within one structure to generate an elliptic motion of surface points. Different concepts based on piezoelectric plates and Langevin transducers are compared. Benefits and drawbacks against the combination of longitudinal and bending modes will be discussed. Numerical results of the stator vibration as well as motor characteristics are validated by measurements on different prototypes. AU - Hemsel, Tobias AU - Mracek, Maik AU - Twiefel, Jens AU - Vasiljev, Piotr ID - 9539 JF - Ultrasonics KW - Piezoelectric linear motor SN - 0041-624X TI - Piezoelectric linear motor concepts based on coupling of longitudinal vibrations VL - 44, Supplement ER - TY - CONF AU - Hemsel, Tobias AU - Priya, S ID - 9540 IS - Band 180 T2 - Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators TI - Model Based Analysis of Piezoelectric Transformers ER - TY - JOUR AB - Piezoelectric transformers are increasingly getting popular in the electrical devices owing to several advantages such as small size, high efficiency, no electromagnetic noise and non-flammable. In addition to the conventional applications such as ballast for back light inverter in notebook computers, camera flash, and fuel ignition several new applications have emerged such as AC/DC converter, battery charger and automobile lighting. These new applications demand high power density and wide range of voltage gain. Currently, the transformer power density is limited to $40 W/cm{^3}$ obtained at low voltage gain. The purpose of this study was to investigate a transformer design that has the potential of providing higher power density and wider range of voltage gain. The new transformer design utilizes radial mode both at the input and output port and has the unidirectional polarization in the ceramics. This design was found to provide 30 W power with an efficiency of 98\% and 30 $\,^{\circ}$C temperature rise from the room temperature. An electro-mechanical equivalent circuit model was developed to describe the characteristics of the piezoelectric transformer. The model was found to successfully predict the characteristics of the transformer. Excellent matching was found between the computed and experimental results. The results of this study will allow to deterministically design unipoled piezoelectric transformers with specified performance. It is expected that in near future the unipoled transformer will gain significant importance in various electrical components. AU - Hemsel, Tobias AU - Priya, S ID - 9541 JF - Ultrasonics KW - Piezoelectric transformers SN - 0041-624X TI - Model based analysis of piezoelectric transformers VL - 44, Supplement ER - TY - JOUR AB - An improved concept for ultrasonic hyperthermia of tumors is presented. This concept is based on past experience of a German government supported project [1], which ended in 1984. It offers a low cost alternative to common RF- and microwave methods for hyperthermia of tumors with volumes between 1 and 40 ml at treatment times between 30 and 60 min. Our new version of the system considerably improves the temperature suppression in the healthy tissue around the target area and enables the adjustment of the beam width to the actual tumor size and the field geometry to the depth and shape of the tumor. The applicator can be used for moderate hyperthermia with tissue overheating up to 10 K or for ablation therapy with short high temperature pulses. Its central area is free for the integration of a commercial ultrasonic diagnostic sector scanner or a Doppler flow sensor in order to support the adjustment of the transducer and to monitor the whole area during the therapy. AU - Lierke, E.G. AU - Hemsel, Tobias ID - 9543 JF - Ultrasonics KW - Moderate hyperthermia SN - 0041-624X TI - Focusing cross-fire applicator for ultrasonic hyperthermia of tumors VL - 44, Supplement ER - TY - CONF AU - Lierke, Ernst-Günter AU - Hemsel, Tobias ID - 9544 IS - Band 180 T2 - Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators TI - Focussing Cross-Fire Applicator for Ultrasonic Hyperthermia of Tumors ER - TY - CONF AU - Mracek, B AU - Hemsel, Tobias AU - Mracek, Maik ID - 9545 IS - Band 180 T2 - Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators TI - Powder Transport by Ultrasonic Waves ER - TY - JOUR AB - Rotary ultrasonic motors have found broad industrial application in camera lens drives and other systems. Linear ultrasonic motors in contrast have only found limited applications. The main reason for the limited range of application of these very attractive devices seems to be their small force and power range. Attempts to build linear ultrasonic motors for high forces and high power applications have not been truly successful yet. To achieve larger force and higher power, multiple miniaturized motors can be combined. This approach, however, is not as simple as it appears at first glance. The electromechanical behaviour of the individual motors differs slightly due to manufacturing and assembly tolerances. The individual motor characteristics are strongly dependent on the driving parameters (frequency, voltage, temperature, pre-stress, etc.) and the driven load and the collective behaviour of the swarm of motors is not just the linear superposition of the individual drive's forces. Thus, the bundle of motors has to be synchronized and controlled appropriately in order to obtain an optimized drive that is not oversized and costly. We have investigated driving and control strategies of a set of linear ultrasonic motors. Our contribution will be divided into three main parts. In part I ultrasonic linear motors will be introduced. In part II driving strategies for a single motor as well as for a bundle of motors will be presented. These concepts will be verified by simulation results and experimental data. In part III a simplified model for the motor's electromechanical behaviour will be given. AU - Mracek, Maik AU - Hemsel, Tobias ID - 9546 JF - Ultrasonics KW - Ultrasonic linear motor SN - 0041-624X TI - Synergetic driving concepts for bundled miniature ultrasonic linear motors VL - 44, Supplement ER - TY - JOUR AU - Mracek, Maik AU - Vasiljev, Piotr AU - Hemsel, Tobias AU - Wallaschek, Jörg ID - 9547 JF - Solid State Phenomena TI - Self configuration of a novel miniature ultrasonic linear motor VL - 113 ER -