Micro electro mechanical systems (MEMS) based on piezoelectric effects are used for diverse applications in sensor and actuator technology, e.g. for microphones or loudspeakers in tablets or smartphones. The development of such systems requires detailed knowledge of the underlying physical effects. Therefore, modelling and numerical simulation based on the finite element method is an important tool in the development process. It allows, e.g. to predict the sound field generated by different actuator designs.

Due to the small dimensions of MEMS structures, the ambient air has considerable impact on their vibration behaviour. Modelling the fluid with a linearized version of the Navier-Stokes equations will allow for precisely describing losses arising from viscous and thermal effects. The fluid-structure interaction will be considered via direct coupling, realized through non-conforming grids, which enables an independent meshing of structure and fluid domains. Piezoelectric materials show distinct non-linear hysteresis behaviour. Especially when the full potential of piezo-electric materials should be exploited, i.e. in operation at high excitation levels, their non-linear behaviour must be considered, which is impossible the approach currently used in industrial practice (Voigt's linear theory of piezoelectricity. Therefore, this project aims to develop a macroscopic, non-linear hysteresis model for piezo-electric materials. The non-linear problem will be solved in the frequency domain by a multi-harmonic approach (harmonic balance method). Thereby, the expected periodic solution is composed as a superposition of several harmonics, and the non-linear coupling between them will be considered. This approach represents an extension of the linear frequency domain analysis, and is already successfully applied in the fields of electromagnetics and fluid mechanics. In the fields of piezo electrics and coupled problems this approach has not been pursued yet.

Initiator of this project is the research group “Measurement and Actuator Technology” under the leadership of Prof. Manfred Kaltenbacher, at the Institute of Mechanics and Mechatronics at the TU Wien, Vienna, Austria. The research group is active in modelling and simulation of MEMS systems. The company USound, with its excellent expertise in the field of piezoelectric MEMS for loudspeakers, and its excellently staffed development team represents the ideal project partner. USound concentrates on the development of innovative, high-quality MEMS-based, piezoelectric audio components, specifically on miniaturised loudspeakers for mobile devices such as tablets, smartphones or audio ear plugs. The modelling and simulation techniques, which will be developed and experimentally validated in the framework of this basic research project, will, thus, find numerous applications in the industry.