@inproceedings{9802, abstract = {{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.}}, author = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}}, booktitle = {{Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop}}, keywords = {{Piezoelectric inertia motor, stick-slip motor, driving signal, velocity, smoothness}}, pages = {{16--18}}, title = {{{High-Velocity Slip-Slip Operation of Piezoelectric Inertia Motors - Experimental Validation}}}, year = {{2013}}, } @article{9803, abstract = {{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.}}, author = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}}, journal = {{Journal of Intelligent Material Systems and Structures}}, keywords = {{Actuator, friction, motor, piezoelectric}}, number = {{11}}, pages = {{1380--1391}}, title = {{{Modelling the friction contact in an inertia motor}}}, doi = {{10.1177/1045389X12474354}}, volume = {{24}}, year = {{2013}}, } @article{9804, abstract = {{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.}}, author = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}}, journal = {{Sensors and Actuators A: Physical}}, keywords = {{Inertia motor}}, pages = {{79 -- 89}}, title = {{{Stick-slip and slip-slip operation of piezoelectric inertia drives - Part II: Frequency-limited excitation}}}, doi = {{10.1016/j.sna.2012.11.043}}, volume = {{200}}, year = {{2013}}, } @article{9805, abstract = {{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.}}, author = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}}, journal = {{Sensors and Actuators A: Physical}}, keywords = {{Inertia motor, Stick--slip drive, Mode of operation, Performance indicator, Velocity maximization, Actuator stroke}}, pages = {{90 -- 100}}, title = {{{Stick-slip and slip-slip operation of piezoelectric inertia drives - Part I: Ideal Excitation.}}}, doi = {{10.1016/j.sna.2012.11.012}}, volume = {{200}}, year = {{2013}}, } @article{9781, abstract = {{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\%.}}, author = {{Al-Ashtari, Waleed and Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}}, journal = {{Smart Materials and Structures}}, number = {{3}}, pages = {{035019}}, title = {{{Frequency tuning of piezoelectric energy harvesters by magnetic force}}}, volume = {{21}}, year = {{2012}}, } @article{9782, abstract = {{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.}}, author = {{Al-Ashtari, Waleed and Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}}, journal = {{Journal of Intelligent Material Systems and Structures}}, number = {{1}}, pages = {{15--23}}, title = {{{Analytical determination of characteristic frequencies and equivalent circuit parameters of a piezoelectric bimorph}}}, doi = {{10.1177/1045389X11430742}}, volume = {{23}}, year = {{2012}}, } @inproceedings{9784, abstract = {{Piezoelectric inertia motors use the inertia of a body to drive it by means of a friction contact in a series of small steps. These motors can operate in ``stick-slip'' or ``slip-slip'' mode, with the fundamental frequency of the driving signal ranging from several Hertz to more than 100 kHz. To predict the motor characteristics, a Coulomb friction model is sufficient in many cases, but numerical simulation requires microscopic time steps. This contribution proposes a much faster simulation technique using one evaluation per period of the excitation signal. The proposed technique produces results very close to those of timestep simulation for ultrasonics inertia motors and allows direct determination of the steady-state velocity of an inertia motor from the motion profile of the driving part. Thus it is a useful simulation technique which can be applied in both analysis and design of inertia motors, especially for parameter studies and optimisation.}}, author = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}}, booktitle = {{Ultrasonics Symposium (IUS), 2012 IEEE International}}, issn = {{1948-5719}}, keywords = {{friction, ultrasonic motors, Coulomb friction model, efficient simulation technique, friction contact, high-frequency piezoelectric inertia motor, motor characteristics prediction, numerical simulation, slip-slip mode, stick-slip mode, time-step simulation, ultrasonic inertia motor, Acceleration, Acoustics, Actuators, Computational modeling, Friction, Numerical models, Steady-state}}, pages = {{277--280}}, title = {{{An efficient simulation technique for high-frequency piezoelectric inertia motors}}}, doi = {{10.1109/ULTSYM.2012.0068}}, year = {{2012}}, } @article{9806, abstract = {{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.}}, author = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}}, journal = {{ACTUATOR 2012 Conference Proceedings}}, keywords = {{Piezoelectric Inertia Motors, Drive Signals, Stick-slip, Slip-slip}}, pages = {{761--764}}, title = {{{Analysis of different operation modes for inertia motors}}}, year = {{2012}}, } @misc{9790, abstract = {{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.}}, author = {{Sextro, Walter and Hunstig, Matthias and Bornmann, Peter and Hemsel, Tobias}}, title = {{{Patent DE10201003395: Anordnung und Verfahren zur mehrdimensionalen Messung von Schwingungen eines Objekts. }}}, year = {{2011}}, } @article{9751, abstract = {{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.}}, author = {{Hunstig, Matthias and Hemsel, Tobias}}, issn = {{1948-5719}}, journal = {{Journal of Korean Physical Society}}, number = {{4}}, pages = {{938--941}}, title = {{{Drive Signals for Maximizing the Velocity of Piezoelectric Inertia Motors}}}, doi = {{10.3938/jkps.57.938}}, volume = {{57}}, year = {{2010}}, } @article{9752, abstract = {{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.}}, author = {{Hunstig, Matthias and Hemsel, Tobias}}, issn = {{1948-5719}}, journal = {{Journal of Korean Physical Society}}, number = {{4}}, pages = {{952--954}}, title = {{{Parameter Identification and Model Validation for the Piezoelectric Actuator in an Inertia Motor}}}, doi = {{10.3938/jkps.57.952}}, volume = {{57}}, year = {{2010}}, } @inproceedings{9753, abstract = {{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.}}, author = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}}, booktitle = {{7. Paderborner Workshop Entwurf mechatronischer Systeme}}, editor = {{Gausemeier, Jürgen and Rammig, Franz and Schäfer, Wilhelm and Trächtler, Ansgar}}, issn = {{0924-4247}}, keywords = {{Piezoelektrischer Trägheitsmotoren}}, pages = {{129--141}}, publisher = {{Heinz Nixdorf Institut, Universität Paderborn}}, title = {{{Anregungskonzepte und Modellierung piezoelektrischer Trägheitsmotoren}}}, volume = {{272}}, year = {{2010}}, } @inproceedings{9754, abstract = {{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.}}, author = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}}, booktitle = {{ACTUATOR 2010 Conference Proceedings}}, issn = {{0924-4247}}, pages = {{657--661}}, title = {{{Improving the Performance of Piezoelectric Inertia Motors}}}, year = {{2010}}, } @inproceedings{9735, abstract = {{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.}}, author = {{Hunstig, Matthias and Hemsel, Tobias}}, booktitle = {{6. Paderborner Workshop Entwurf mechatronischer Systeme}}, editor = {{Gausemeier, Jürgen and Rammig, Franz and Schäfer, Wilhelm and Trächtler, Ansgar}}, issn = {{1948-5719}}, keywords = {{Piezoelektrischer Tr{\}}, pages = {{85--96}}, publisher = {{Heinz Nixdorf Institut, Universität Paderborn}}, title = {{{Modellbasierte Entwicklung piezoelektrischer Trägheitsmotoren}}}, volume = {{250}}, year = {{2009}}, }