| Summary: | 碩士 === 國立高雄第一科技大學 === 機械與自動化工程所 === 98 === This study presents the system modeling of a triaxial microaccelerometer consisted of a quadri-beam suspension, a seismic mass, and displacement transducers using piezoelectric thin films. Both suspension beams support two ends of the seismic mass fabricated by anisotropic etching of silicon. An out-of-plane acceleration will result in a symmetric bend, and in-plane accelerations will produce asymmetric bend and torsion of the suspension beams. All of transducers are interconnected such that triaxial accelerations can be measured selectively. The bending rigidity of the suspension beams are derived using the theory of composite beams, and the effective mass and rotational moment of inertia of the supported beams can be determined by kinetic energy method. Using Castigliano''s second theorem and Hooke''s law derive structure stiffness. The formulations of resonant frequencies and sensor sensitivities to tri-axial acceleration are presented. Finally, finite element analysis is applied to verify the analytical results of the frequency response. The error for the resonant frequency and the output sensitivity are all within 4%, which demonstrates the model accuracy. The modeling error increases as the ratio of piezoelectric layer to silicon substrate increases. Assume the maximum error to be 10%, the thickness ratio of the piezoelectric layer to the silicon substrate should be less than 1:6.
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