Structure Design And Performance Analysis Of High-G Piezoresistive Micro-Accelerometer
Date Issued
2014
Date
2014
Author(s)
Tang, Hsin
Abstract
Micro-accelerometer is a tiny sensing component which can convert as well as output acceleration into analog signals. Over the past decade, the technique of semiconductor process has been greatly improved. Since the MEMS processing is compatible with the CMOS manufacturing, the cost of producing micro sensors thus has been reduced; withal, the micro sensors have turned to be more reliable, and the measuring range of acceleration has widened. Hence, micro-accelerometers have become the first commoditized products that grow the rapidest in MEMS. With different measuring range of various designs, micro-accelerometers have been applied widely in daily life, ranging from aerospace technology and military weapons to vehicles, cell phones, and video games of everyday life. The application of micro-accelerometer is everywhere.
In this thesis, micro-accelerometer that is developed by MEMS process can be operated from 0 to 10,000 G impact. This micro-accelerometer can continuously sense the acceleration which the carrier undergoes and simultaneously output analog signals. In order to reduce research costs, three kinds of micro-accelerometer are designed with different sizes of cantilever beams: 80μm, 100μm, and 120μm in accordance to documents and theories. First, piezoresistor is selected as the component to sense acceleration and use the software for numerical simulation to analyze, on condition that given the same high G shock acceleration, observe the change of stress and output voltage that each structural element. Considering both the range of change and the usual frequency of structural stress, adjust the design of detailed fine-tuning, ensuring the components will not be damaged and will effectively gain sensitivity towards output signals.
The micro-accelerometer that is designed based on the former numerical simulation can endure 120MPa at most which is yet reaching the yield strength of silicon. The change of voltage could be up to mV level, and subsequently, the amplifier enables the sensitivity to meet the anticipation. The first resonant frequency of the sensor structure is 76kHz. Since the first resonant frequency is much higher than the main frequency 4.8kHz of input wave, it avoids the possibility of the input wave causing resonance and distortion.
The micro-accelerometer designed by MEMS manufacturing process and mask made based on the whole manufacturing process, use micro-nanometer process technology for electromechanical trial. Eventually, after segmentation and packaging, the designed micro-acceleration sensor is successfully made. These sensors will be arranged on a centrifugal machine which can produce a steady acceleration ranged from 0 to 10,000G by adjusting the spin rate of a turning table where the sensor is mounted. The steady acceleration allows calibrations of linearity and sensitivity of the devices. Experimental results show that the sensitivity of the accelerometer is up to 1.92μV/V/G between0~ 4500G,even the sensitivity of design that size of cantilever beam is 120μm can be reached 1.54μV/V/G.
Since the accelerometer are made by semiconductor process, the production could be divided into several times. Consequently, the quality is equal, and the cost per unit is much lower than the products that are made in the way of machining. Moreover, due to the small capacity and the lightness of the acceleration sensor, the size as well as weight of fuse can be shrunk and becomes more resistant to impact.
Subjects
加速度偵測器
微機電製程
高G衝擊模擬
動態響應
Type
thesis
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