Two-axis resonant silicon micro-accelerometer

Abstract

The invention discloses a frequency detection principle-based two-axis resonant silicon micro-accelerometer, which consists of an upper layer and a lower layer. The upper layer is an accelerometer mechanical structure manufactured on a monocrystalline silicon slice; the lower layer is a signal lead manufactured on a glass substrate; the accelerometer mechanical structure consists of a mass block, an outer frame, two pairs of identical resonators and eight identical first-stage lever amplification mechanisms; the mass block is positioned in the middle of the structure; one pair of resonators is symmetrically arranged on the upper and lower sides of the mass block and is used for measuring acceleration input along a y axis; the other pair of resonators is symmetrically arranged on the left and right sides of the mass block and is used for measuring acceleration input along an x axis; and the whole structure is centrosymmetric. The micro-accelerometer is not required to be supported by a supporting beam, so that the structure is simplified; and the micro-accelerometer has a stable structure, and inertia force converted from the acceleration is effectively transferred to the resonators simultaneously.

Description

technical field [0001] The invention belongs to micro-inertial sensor technology in MEMS, in particular to a dual-axis resonant silicon micro-accelerometer. Background technique [0002] Resonant silicon micro accelerometer is a typical MEMS inertial sensor. Its research began in the early 1970s, and there are various forms such as capacitive, piezoelectric, piezoresistive, thermal convection, tunnel current and resonance. The unique feature of the resonant silicon micro accelerometer is that its output signal is a frequency signal, and its quasi-digital output can be directly used in complex digital circuits, which has high anti-interference ability and stability, and eliminates the need for other types of acceleration In order to avoid the inconvenience of signal transmission, it is directly connected to the digital processor. At present, the research of resonant accelerometer by Draper Laboratory in the United States is in the leading position in the world. The micro-mec...

AI Technical Summary

Problems solved by technology

The structure is composed of a mass block, a support beam, a tuning fork and a mechanical amplification system. The mass block is in the shape of a "back", and the four tuning forks are located in the middle of the mass block and arranged symmetrically in the center, which overcomes the disadvantage of low utilization of the mass block. At the same time, the influence of material inhomogeneity and ambient temperature on the four tuning forks is the same, and the influence of ambient temperature on device performance can be eliminated through differential detection, but in fact, the processing error makes the resonant frequencies of the four symmetrical resonators not completely equal. The thermal stress on the four resonators is also different, so the influence of thermal stress cannot be eliminated by means of differential detection

The four resonators of this structure are directly connected to the fixed base, and the processing residual stress and thermal stress have a great influence on the resonant frequency, so that the frequency temperature coefficient of the speedometer is relatively large

The "back"-shaped mass block is affected by machining errors, and it is easy to form mass eccentricity, resulting in excessive sensitivity of the x-axis and y-axis cross-axis

Moreover, the four tuning forks of this structure are arranged adjacent to each other, and the electrical coupling is relatively large. When the resonant frequencies of the resonators are similar, adjacent frequency interference will occur, which will reduce the sensitivity of the accelerometer.

And the four resonators of this structure have no isolation structure, and the x and y axis cross sensitivity is large

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