Design, microfabrication, and control of high-performance micromachined tunneling accelerometers

High-precision accelerometers are widely required in applications such as microgravity measurements, acoustic measurements, seismology for oil exploration and earthquake prediction, platform stabilization in space, navigation and guidance. Among these high-precision measurement applications MEMS accelerometers are seldom adopted, even though miniature accelerometers would be preferred. One of the important reasons is the generally poor resolution of these miniature accelerometers due to the constraints of scaling laws. Miniature accelerometers suffer from either poor resolution or very narrow measurement bandwidth. It has proven difficult to make miniature accelerometers based on piezoresistive, piezoelectric or capacitive transducers to achieve both sub-micro- g resolution and over 1 kHz bandwidth.; Displacement transducers based on quantum electron tunneling have been demonstrated in a variety of physical sensors because of high sensitivity. For several years, miniature-tunneling accelerometers have been studied by researchers at several institutions and in industry. Some of this work has been motivated by the ONR requirement for an accelerometer with a 10 nano- g/$Hz$ resolution from 5 Hz to 1 kHz. Analysis of tunneling sensors shows that this performance should be accessible, but practical problems in sensor construction and operation have always prevented this goal from being met.; To meet the resolution and size requirements, we utilize MEMS fabrication techniques to fabricate the miniature tunneling accelerometers. To operate our tunneling accelerometers and enhance their performance, we developed and implemented three controllers based on LQG, $H\infty$ and mixed μ synthesis technologies, respectively. These controller designs were carried out at different development stages and have different advantages and focuses.; This doctoral work presents the design, microfabrication and system control of miniature tunneling accelerometers that approach the high performances of both a 20 nano-g/$Hz$ resolution and a 1.5 kHz bandwidth. These accelerometers may be packaged in an 8-cm3-sphere volume with a total mass of 8 grams to allow neutral buoyancy in the ocean at 1 km depth. Together, the achievement of their performance level over their frequency range in this research is unprecedented in any accelerometers of similar or smaller size. The successful applications of these three areas, MEMS fabrication, quantum electron tunneling, and control technology, make this research goal feasible.