Issue 29

V. Zega et alii, Frattura ed Integrità Strutturale, 29 (2014) 334-342; DOI: 10.3221/IGF-ESIS.29.29 334 Focussed on: Computational Mechanics and Mechanics of Materials in Italy Integrated structure for a resonant micro-gyroscope and accelerometer V. Zega, C. Comi, A. Corigliano Department of Civil and Environmental Engineering, Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano, Italy. valentina.zega@polimi.it, claudia.comi@polimi.it , alberto.corigliano@polimi.it C. Valzasina AMS Division, STMicroelectronics, via Tolomeo 1, 20010 Cornaredo, (Milano), Italy carlo.valzasina@st.com A BSTRACT . This paper presents the study of the mechanical behavior of a microstructure designed to detect acceleration and angular velocity simultaneously. The new resonant micro-sensor proposed, fabricated by the ThELMA © surface-micromachining technique, bases detection of two components of external acceleration (one in-plane component and one out-of plane component) and two components of angular velocity (roll and yaw) on the variation of frequency of several elements set in resonance. The device, despite its small dimensions, provides a differential decoupled detection of four external quantities thanks to the presence of four slender beams resonating in bending and four torsional resonators. K EYWORDS . MEMS; Gyroscope; Accelerometer; Resonators. I NTRODUCTION icro-Electro-Mechanical Systems (MEMS) or microsystems, are micro-sized devices (see e.g. [1, 2]) nowadays largely used in the consumer and automotive market. Their diffusion is exponentially increasing in the biomedical market; their use is also growing in structural engineering as efficient and low-cost devices for structural health monitoring. Typical examples of widely diffused MEMS are accelerometers, gyroscopes, pressure sensors. The fast evolution of MEMS technology is mainly driven by the attempt to reduce the total size of the microsystem, while keeping the power consumption low and the sensitivity high enough for the specific applications. To reduce the cost and the dimensions required to embed several sensors for detecting the various external quantities, there is a trend to integrate a number of detection structures within the same device. Several proposals consists in integrating in a single die several sensors with different proof masses, a review of multi-DOF inertial MEMS is presented in [3]. Some interesting proposals also exist of multi-axial inertial sensors with a single proof mass: in [4] a five-axis sensor (3-axis accelerometer and 2-axis gyroscope) with capacitive detection was fabricated using silicon bulk micromachining; in [5] a six-axis vortex sensor (3-axis accelerometer and 3-axis gyroscope) with piezo-resistive detection was proposed. In this line of research, in the present work we study an integrated structure for a micro-gyroscope and accelerometer. The device is fabricated by the Thelma © surface-micromachining technique [6] that makes it possible to obtain planar suspended structures with relatively small thickness, anchored to the substrate through flexible parts (springs) and M

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