| Summary: | 博士 === 國立臺灣大學 === 應用力學研究所 === 103 === This research developed a microaccelerometer via Computer-Aid-Design(CAE) and Micro Electro Mechanical Systems(MEMS) with high performance in linearity and cross-axis sensitivity. Unlike the conventional sensing elements which are always embedded at the position of maximum displacement, the present study situated the sensors at the locations where the maximum displacements of the structure are generated in order to raise up the maximal output than the former.
The core elements of accelerometer includes a vertical, double-ended flexural beam, a proof mass integrated at the middle section of the beam, and four suspended piezoresistors fixed at the mass block and across the trenches to the anchor pads. The mass block had maximum displacements of the dynamic structure which would activate the sensors to deliver maximal output. It was simulated by numerical method to analyze how much and where the maximal stress would be. The sensing chip was fabricated on a silicon-on-insulator(SOI) wafer through MEMS processes and installed by Dual-In-Package. The accelerometer was placed on a rate table that provided stable centrifugal acceleration up to approximately 3000 G for quasi-static testing. The output voltage of the accelerometer was digitized and radiofrequency transmitted for remote data acquisition.
The natural frequency was about 232.4 kHz from mode analysis. After numerous experiments, the correlations for the individual runs showed that the accelerometer had a sensitivity of 3.0015 μV/Vexc/G with extraordinary performance. The best linearity of the sensing output was only 0.11% of full scale output (FS, or 59 dB), as deduced from the average standard deviation of all test runs. The average of the maximum reading deviations from the corresponding correlated curves was approximately 0.26% FS. Moreover, the cross-axis sensitivity for the two orthogonal directions nearly vanished in the test range. With the high rigidity of the microstructure, the accelerometer exhibited an ultra high performance factor of 25.8 x 10^6 MHz. The accelerometer possessed exceptional sensitivity, linearity, and repeatability, and extremely low cross-axis interference and noise.
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