Micro Electro Mechanical Systems (MEMS) are the new and emerging technology of the future and have many applications on different disciplines like biomedical, imaging technology, biology etc. Characterization of motion and vibrations of such systems early in the design process can impact the quality and reliability of the design. This paper presents the modeling, testing, and validation methodologies developed to predict the dynamic performance of micro systems. A two-dimensional torsional micro scanner mirror is chosen as the case study to demonstrate the developed methodologies. The finite element model of the micro mirror is built using ANSYS software. ANSYS modal analysis results, which are eigenvalues (natural frequencies) and eigenvectors (modeshapes), are used to characterize the vibrational behavior of the mirror. An experimental vibration testing system is built to validate, update, and correct the finite element model. The testing system for measuring the out-of-plane velocity profile of the device includes a laser doppler vibrometer (LDV) that is used to pick up signals without contacting the micro structure. The sensor head utilizes flexible fiber-optics and an output lens to deliver the laser probe to the measurement point and to collect the reflected light as an input to the interferometer. The micro mirror is excited at a wide frequency range and the velocity data measured by LDV is collected through the use of a data acquisition card and a LabView program that is developed in our laboratory. The transfer functions that relate the excitation input to velocity output are measured at various locations of the micro structure and then transferred to a modal analysis software, ME’scopeVES, to extract the modal parameters. The testing system for measuring the in-plane motion uses the stroboscopic illumination method. The system combines conventional optical components (macrozoom lens) and a light-emitting diode (LED) stroboscope with incremental phase shifts. The system drives a digital camera to capture a sequence of the moving micro structure “frozen” by the strobe LED at different spaced phases. Additionally, a pulse/delay and a signal generator are used to synchronize the signals that drive the LED, the camera and the test specimen. The in-plane motion of the micro mirror can be estimated by using some image processing algorithms. Finally, the finite element model of the micro mirror is updated and corrected based on the in-plane and out-of-plane measurements.
Journal: TechConnect Briefs
Volume: 3, Technical Proceedings of the 2006 NSTI Nanotechnology Conference and Trade Show, Volume 3
Published: May 7, 2006
Pages: 594 - 597
Industry sector: Sensors, MEMS, Electronics
Topic: MEMS & NEMS Devices, Modeling & Applications