Design and Modeling of MEMS Inertial Sensors

Abstract

This thesis is about MEMS inertial sensors specially gyroscopes. This topic is considered as a hot research point due to it’s wide range of applications starting from consumer de- vices ending by strategic applications such as military and aerospace. MEMS gyroscopes have a great advantage over conventional mechanical and optical gyroscopes concerning size, power, cost and reliability. Unfortunately, they face a great challenge in achieving high performance. This work tries to explore different design techniques to increase MEMS gyroscopes performance. In addition, it provides accurate design models and optimization for different MEMS structures. The thesis is divided into Five chapters as listed below:

Chapter 1

This is an introductory chapter that shows the motivation and the target of this work. It focuses on the scope of this thesis and clarifies its organization flow.

Chapter 2

This chapter contains most of the required information about MEMS inertial sensors, especially gyroscopes. It starts with market study and survey for different MEMS appli- cations. Then, it focuses on the inertial sensors explaining their principles of operation, specifications and briefly summarizes the system elements. Moreover, the author ex- plains the different modes of operation of MEMS gyroscopes.

Chapter 3

In this chapter, the author demonstrates the design, modeling and simulation of the me- chanical elements of MEMS gyroscopes. We implemented a new optimization algorithm x

for the design of Fish-Hook shaped spring which is widely used in state-of-the art MEMS tuning fork gyroscopes. We derived closed form equations for stiffness and resonance frequency of the four effective vibrations eigen mode considering the model limitations. Finally, We Developed a design tool using MATLAB for the design and optimization of tuning fork gyroscope structure using Fish-Hook shaped spring. In addition, the chapter includes the simulation, fabrication and testing of this structure.

Chapter 4

This chapter illustrated the Design of MEMS gyroscopes on the system level and the structural elements affecting the gyroscope modes of operation. In this chapter, the author introduces a novel mode of operation called ”Staggered Mode” for MEMS gy- roscopes that optimizes the bandwidth-sensitivity relation. We added a modification on a decoupled gyroscope structure to adopt this mode based on the previously mod- eled Fish-Hook MEMS spring. we designed and implemented the modified structure that was later fabricated using SOIMUPS process occupying 2.7 × 4.4mm2. The testing showed that the staggering has the capability to achieve a maximally flat band with enhancement more than 40% compared to that of matched mode while achieving better sensitivity by Qsns

Chapter 5

In this chapter, we conclude on the modeling, simulation and design. In addition, the chapter contains a summary of the potential future work need to develop the proposed ideas.

Key words: MEMS, Gyroscope, Coriolis, Fish-Hook, Mode Decoupling, Staggered Mode