Investigations on novel platforms of micro electro mechanical inertial sensors: Analysis, construction and experimentation.

摘要

Inertial sensors, such as gyroscopes and accelerometers, are widely used in automotive, biomedical and military industries. Shrinking the scale of micro electro mechanical inertial sensors (MEMIS) increments their spectrum of possible applications. This dissertation investigates platforms for performance enhancement of a micro gyroscope and a tunneling accelerometer.; A very sensitive method of measuring linear acceleration is to exploit the exponential dependence of a tunneling current, usually of the order of a few nano-amperes, on the distance between a tip and an electrode, of the order of a few A. In this dissertation, a lateral tunneling accelerometer is designed, fabricated, and characterized. To maintain such a small distance constant and to reject external disturbances requires the use of closed-loop feedback. The effect of different noise sources on a tunneling accelerometer is analyzed using a state space stochastic representation, and the controller integration in a digital flexible platform is presented.; Additionally, the sensitivity loss, commonly presented in traditional micro gyroscopes based on harmonic oscillators, is overcome by using parametric resonance as an actuation mechanism. Differences in dimensions, which are always present due to fabrication imperfections, lead to a mismatch in fundamental frequencies between the orthogonal modes of the micro structure. In harmonic oscillator based micro gyroscopes, this mismatching results in drastic loss of sensitivity.; The resonant Coriolis force sensor proposed is a 2-DOF structure in which the drive-mode consists of a 1-DOF oscillator governed by a nonlinear Mathieu equation and the sense-mode is a 1-DOF oscillator governed by a Duffing model, both of them coupled by the Coriolis force. Analytical and experimental results presented in this thesis have shown that when the driving frequency is near twice the fundamental resonance of the drive-mode, a small parametric excitation can produce a large response over a range of frequencies and the amplitude is not dependent on the damping term as in the harmonic case. Therefore differences in drive and sense modes frequencies do not compromise the sensitivity in 1kHz range. Thus, the unique properties of parametric resonance make the micro gyroscope inherently robust to parameter variations over a wide spectrum.