Abstract

A novel micromachined z-axis torsional accelerometer based on the tunneling magnetoresistive effect is presented in this paper. The plane main structure bonded with permanent magnetic film is driven to twist under the action of inertial acceleration, which results in the opposite variation of the magnetic field intensity. The variation of the magnetic field is measured by two differential tunneling magnetoresistive sensors arranged on the top substrate respectively. Electrostatic feedback electrodes plated on the bottom substrate are used to revert the plane main structure to an equilibrium state and realize the closed-loop detection of acceleration. A modal simulation of the micromachined z-axis tunneling magnetoresistive accelerometer was implemented to verify the theoretical formula and the structural optimization. Simultaneously, the characteristics of the magnetic field were analyzed to optimize the layout of the tunneling magnetoresistance accelerometer by finite element simulation. The plane main structure, fabricated with the process of standard deep dry silicon on glass (DDSOG), had dimensions of 8000 μm (length) × 8000 μm (width) × 120μm (height). A prototype of the micromachined z-axis tunneling magnetoresistive accelerometer was produced by micro-assembly of the plane main structure with the tunneling magnetoresistive sensors. The experiment results demonstrate that the prototype has a maximal sensitivity of 1.7 mV/g and an acceleration resolution of 128 μg/Hz0.5 along the z-axis sensitive direction.

Highlights

  • Microelectromechanical (MEMS) inertial sensors are small, robust and cheap, ideal candidates for applications from navigation to automotive [1–5]

  • Another novel method of acceleration measurement was based on tunneling magnetoresistance, including a tunneling magnetoresistive (TMR) sensor that was used to precisely measure the magnetic field and a micro-cantilever beam bonded with the cylinder permanent magnet, which converted input acceleration to magnetic field changes

  • This paper presents a novel micromachined z-axis torsional accelerometer based on the tunneling magnetoresistive effect, which is mainly composed of the top substrate, the middle plane main structure and the bottom substrate

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Summary

Introduction

Microelectromechanical (MEMS) inertial sensors are small, robust and cheap, ideal candidates for applications from navigation to automotive [1–5]. A micromachined z-axis tunneling magnetoresistive accelerometer based on microfabrication and micro-assembly technology has been proposed, with a noise floor of 86.2 μg/Hz0.5, in the literature [27]. Another novel method of acceleration measurement was based on tunneling magnetoresistance, including a tunneling magnetoresistive (TMR) sensor that was used to precisely measure the magnetic field and a micro-cantilever beam bonded with the cylinder permanent magnet, which converted input acceleration to magnetic field changes. This paper presents a novel micromachined z-axis torsional accelerometer based on the tunneling magnetoresistive effect, which is mainly composed of the top substrate, the middle plane main structure and the bottom substrate.

Structure Principle
Simulation Analysis
Measurement and Control Circuit
Experiment
Conclusions
Full Text
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