@proceedings{9553,
  abstract     = {{In the design process of energy harvesting systems based on piezoelectric elements, achievable energy output is the most interesting factor. To estimate this amount a priori manufacturing of prototypes a mathematical model is very helpful. Within this contribution we will introduce a model based on electro-mechanical circuit theory. Its parameters are identified by measurements and the model is validated by comparison to experimental results. The model is designed to support the development-engineer in the dimensioning of energy harvesting units to specific application demands. Two main challenges in device design are investigated with the mathematical model: influence of the ambient excitation frequency, and influence of the load impedance. Typically, the equivalent model approach delivers models for piezoelectric elements that are driven in resonance by electrical excitation. In the case of energy harvesting the piezoelectric elements are excited mechanically and most often non-resonant. Thus, we first set up a mechanical equivalent model for base excited systems. In first approximation it represents an energy harvesting unit around one resonance frequency. The model is expandable for a wider frequency range using the superpositioning of multiple circuits. From the viewpoint of optimum energy transformation between mechanical and electrical energy it is favorable to drive piezoelectric elements at resonance or anti-resonance. Thus, an energy harvesting system should be tuned to the excitation frequency.}},
  editor       = {{Twiefel, Jens and Richter, Björn and Hemsel, Tobias and Wallaschek, Jörg}},
  pages        = {{616909--616909--10}},
  title        = {{{Model-based design of piezoelectric energy harvesting systems}}},
  doi          = {{10.1117/12.658623}},
  volume       = {{6169}},
  year         = {{2006}},
}

@inproceedings{9558,
  author       = {{Wilmanns, S and Nakamura, K and Mracek, Maik and Hemsel, Tobias}},
  booktitle    = {{Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators}},
  pages        = {{205}},
  title        = {{{Non-resonant piezoelectric motors driven in audible frequency range}}},
  volume       = {{Band 180}},
  year         = {{2006}},
}

@inproceedings{9559,
  author       = {{Zhou, W and Fu, Bo and Hemsel, Tobias and Wallaschek, Jörg}},
  booktitle    = {{Proceedings of 2nd International Workshop on Piezoelectric Materials and Applications in Actuators}},
  pages        = {{213}},
  title        = {{{Piezoelectrics in dental tools}}},
  volume       = {{Band 180}},
  year         = {{2006}},
}

@inproceedings{15348,
  abstract     = {{In spite of the outstanding importance of neuronavigational techniques the neurosurgeon has still highly to rely on his visual as well as tactile sense and his experience in distinguishing tumor tissue from intact brain parenchyma. All the more - as neuronavigation is based on preoperative imaging scans - considerable brain shift may occur during surgery and that will lead to erroneous results. Furthermore the surgeon loses his tactile sense during endoscopic surgery. Therefore control of tissue manipulation is limited today to the fiberoptic image techniques, possibly ensured by neuronavigational supervision or haptic feedback systems. In robotic guided surgery the missing tactile sensing will be particularly crucial. The human sense of touch is a highly complex sensory perception comprising epicritical and propiozeptive information processing. The development of a tool for intraoperative tactile perception will be a highly challenging task to improve the safety during surgery. Different sensor concepts (elasticity probe and resonant piezoelectric sensor) have been set up and adapted to distinguish elasticity differences in soft tissue mimicking gel phantoms. The elasticity probe is based on two leaf springs of different bending stiffness. The two tips of the beams act both on the material to be tested. The two deflections measured by strain gauges are processed in a mathematical model calculating the phantoms' stiffness. In contrast to this differential sensing concept the piezoelectric sensor, which is driven at its resonance, measures stiffness and damping of the phantoms by evaluating frequency or phase shift and amplitude change. Gelatine gels of different concentrations (5{\%}, 10{\%}, 20{\%} of gelatine) have been used for a characterization of sensor elements and their sensitivity to elasticity distinctions. Using the hand-guided elasticity probe the determination of gel elasticity is performed with high reliability. By constant mechanical load the piezoelectric sensor also presents a proportional dependency of tissue elasticity.}},
  author       = {{Kehl, Romina and Stroop, Ralf and Oliva Uribe, David and Hemsel, Tobias and Henning, Bernd}},
  location     = {{Hannover}},
  title        = {{{Tactile sensors for determination of elastic properties of brain tissue mimicking phantoms}}},
  year         = {{2006}},
}

@inproceedings{9527,
  author       = {{Hemsel, Tobias}},
  booktitle    = {{Mechatronik 2005 Innovative Produktentwicklung}},
  number       = {{Band 2}},
  pages        = {{1013--1032}},
  title        = {{{Modellgestützte Analyse piezoelektrischer Transformatoren}}},
  volume       = {{1892}},
  year         = {{2005}},
}

@inproceedings{9528,
  author       = {{Hemsel, Tobias and Mracek, Maik and Twiefel, Jens and Vasiljev, Piotr and Wallaschek, Jörg}},
  booktitle    = {{Proceedings of the First International Conference on Ultrasonic Motors and Actuators (IWOUMA)}},
  pages        = {{32--36}},
  title        = {{{Linear ultrasonic motors based on coupling of longitudinal vibrations}}},
  year         = {{2005}},
}

@inproceedings{9530,
  author       = {{Mracek, Maik and Hemsel, Tobias and Wallaschek, Jörg}},
  booktitle    = {{Proceedings of the First International Conference on Ultrasonic Motors and Actuators (IWOUMA)}},
  pages        = {{23--24}},
  title        = {{{Parallel Operation of Ultrasonic Linear Motors}}},
  year         = {{2005}},
}

@inproceedings{9531,
  author       = {{Twiefel, Jens and Hemsel, Tobias and Kauczor, Christopher and Wallaschek, Jörg}},
  booktitle    = {{6th International Workshop on Research and Education in Mechatronics}},
  pages        = {{356--361}},
  title        = {{{Teaching Mechatronics to a Mixed Audience from Industry and University}}},
  year         = {{2005}},
}

@misc{52642,
  author       = {{Wallaschek, J. and Hemsel, Tobias and Mracek, M.}},
  isbn         = {{3-935433-89-1}},
  title        = {{{Proceedings of the 2nd International Workshop on Piezoelectric Materials and Applications in Acutators}}},
  volume       = {{Band 180}},
  year         = {{2005}},
}

@inproceedings{8951,
  author       = {{Fu, Bo and Hemsel, Tobias and Wallaschek, Jörg}},
  booktitle    = {{Proceedings of the 18th International Congress on Acoustics, ICA}},
  pages        = {{4--9}},
  title        = {{{Model-based Diagnosis for Sandwiched Ultrasonic Transducers}}},
  year         = {{2004}},
}

@inproceedings{8953,
  author       = {{Hemsel, Tobias}},
  booktitle    = {{Proceedings of the First International Conference on Ultrasonic Motors and Actuators (IWOUMA)}},
  title        = {{{Linear piezoelectric motors and their application}}},
  year         = {{2004}},
}

@inproceedings{9519,
  abstract     = {{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 controlled to get an optimized drive that is not oversized and costly.}},
  author       = {{Hemsel, Tobias and Mracek, Maik and Wallaschek, Jörg and Vasiljev, Piotr}},
  booktitle    = {{Ultrasonics Symposium, 2004 IEEE}},
  issn         = {{1051-0117}},
  keywords     = {{drives, electromechanical effects, linear motors, ultrasonic motors, car sunroof, car window, electromechanical behavior, high power ultrasonic linear motors, multiple miniaturized motors, positioning tasks, translatory drive, Costs, Electromagnetic forces, Frequency, Laboratories, Manufacturing, Mechatronics, Micromotors, Ultrasonic imaging, Vibrations, Voltage}},
  number       = {{Vol.2}},
  pages        = {{1161--1164}},
  title        = {{{A novel approach for high power ultrasonic linear motors}}},
  doi          = {{10.1109/ULTSYM.2004.1417988}},
  volume       = {{2}},
  year         = {{2004}},
}

@inproceedings{9521,
  author       = {{Littmann, Walter and Hemsel, Tobias and Wallaschek, Jörg}},
  booktitle    = {{Proceedings of the 18th International Congress on Acoustics}},
  pages        = {{2889--2892}},
  title        = {{{Design criteria for piezoelectric transformers}}},
  volume       = {{4}},
  year         = {{2004}},
}

@inproceedings{9522,
  author       = {{Mracek, Maik and Wallaschek, Jörg and Hemsel, Tobias}},
  booktitle    = {{Proceedings of the 18th International Congress on Acoustics}},
  pages        = {{417--420}},
  title        = {{{Self configuration of miniature ultrasonic linear motors}}},
  year         = {{2004}},
}

@inproceedings{9524,
  author       = {{Fu, Bo and Hemsel, Tobias and Wallaschek, Jörg}},
  booktitle    = {{Proceedings of the 18th International Congress on Acoustics, ICA}},
  pages        = {{4--9}},
  title        = {{{Model-based Diagnosis for Sandwiched Ultrasonic Transducers}}},
  year         = {{2004}},
}

@inproceedings{8935,
  author       = {{Hemsel, Tobias and Wallaschek, Jörg}},
  booktitle    = {{Proceedings of the 5th International Congress of Intelligent Materials (ICIM)}},
  title        = {{{Modelling and Analysis of Piezoelectric Transformers}}},
  year         = {{2003}},
}

@inproceedings{8936,
  author       = {{Littmann, Walter and Hemsel, Tobias and Kauczor, Christopher and Wallaschek, Jörg and Sinha, W}},
  booktitle    = {{Proceedings of World Congress Ultrasonics}},
  pages        = {{547--550}},
  title        = {{{Load-adaptive phase-controller for resonant driven piezoelectric devices}}},
  year         = {{2003}},
}

@inproceedings{8926,
  abstract     = {{Piezoelectric transformers are well known since the publication of some patent applications at the end of the 1950s. But until today their only business use lies in the field of backlighting systems for LCDs. Due to key features as light-weight, flatness, high step-up at low volume and high efficiency piezoelectric transformers should be usable in a much broader range of applications. This contribution returns to mind their operating principle, shows how to model and to develop such devices as well as give some aspects for development trends that will lead to further applications.}},
  author       = {{Hemsel, Tobias and Littmann, Walter and Wallaschek, Jörg}},
  booktitle    = {{Ultrasonics Symposium, 2002. Proceedings. 2002 IEEE}},
  issn         = {{1051-0117}},
  keywords     = {{piezoelectric devices, reviews, transformers, backlighting systems, flatness, high efficiency piezoelectric transformers, high step-up, light-weight, low volume, operating principle, piezoelectric transformers, Circuits, Costs, Electromagnetic devices, Electromagnetic fields, Mechanical energy, Piezoelectric materials, Power electronics, Switching frequency, Transformers, Vibrations}},
  number       = {{vol.1}},
  pages        = {{645--648}},
  title        = {{{Piezoelectric transformers - state of the art and development trends}}},
  doi          = {{10.1109/ULTSYM.2002.1193485}},
  volume       = {{1}},
  year         = {{2002}},
}

@inproceedings{8927,
  author       = {{Hemsel, Tobias and Littmann, Walter and Wallaschek, Jörg}},
  booktitle    = {{47. Internationales Wissenschaftliches Kolloquium}},
  title        = {{{Piezoelektrische Transformatoren - Bauformen und Modellierung}}},
  year         = {{2002}},
}

@inproceedings{8925,
  author       = {{Wallaschek, Jörg and Hemsel, Tobias}},
  booktitle    = {{Special Antriebstechnik}},
  pages        = {{70--71}},
  title        = {{{Piezoelektrische lineare Schwingungsantriebe}}},
  year         = {{2001}},
}