Design and Analysis of a MEMS Vibration Sensor for Automotive Mechanical Systems

Abstract

This thesis presents the theoretical analysis and experiment results of MEMS sensors designed for the application of low frequency vibration sensing. Each sensor consists of a proof mass connected to a folded beam micro-flexure, with an attached capacitive comb drive for displacement sensing. Three comb drive arrangements are evaluated, the transverse, lateral, and tri-plate differential. The sensors are fabricated using the well developed foundry processes of PolyMUMPS and SoiMUMPS. In addition, a capacitance to voltage readout circuit is fabricated using discrete components. Static tests, evaluating the capacitance to displacement relation, are conducted on a six degree of freedom robotic manipulator, and dynamic tests evaluating the sensor response to sinusoidal excitations are conducted on a vibrating beam. The end use of the sensor involves real-time vibration monitoring of automobile mechanical systems, such as power seats, windshield wipers, mirrors, trunks, and windows, allowing for early detection of mechanical faults before catastrophic failure.