| Microelectromechanical systems（MEMS）inertial sensors（such as accelerometers and gyroscopes）have high performance,low power consumption,low chip cost,high integration,high reliability,small size,and light weight,and are now used in the daily life of a wide range of consumers.Currently,there is an increasing demand for triaxial MEMS accelerometers in various fields,and capacitive MEMS accelerometers have higher accuracy and lower temperature coefficient compared to piezoresistive and piezoelectric accelerometers,thus the design of triaxial capacitive MEMS accelerometers is especially significant.The research of triaxial capacitive MEMS accelerometer is mainly to solve the following two problems: one is to study how to reduce the impact of cross-crosstalk on the measurement accuracy;the other is to study how to achieve high sensitivity and large enough range,both are the performance index of triaxial capacitive MEMS accelerometer,Therefore,it is significant to design and study a triaxial capacitive MEMS accelerometer with high sensitivity and large range while reducing cross-crosstalk.In this thesis,based on the principle of Newton’s second law,MEMS accelerometer is modeled in a simplified way,the performance parameters of the accelerometer are analyzed,and the capacitance detection method and damping analysis of the accelerometer are described in detail.On this basis,a three-mass block three-axis MEMS capacitive accelerometer structure with a range of ± 16 g is designed,simulated and optimized,and a three-axis MEMS capacitive accelerometer structure with a range of ± 50 g is designed and simulated and optimized to improve the comprehensive performance of sensitivity and range.In addition,a preliminary design of the experimental process of the accelerometer is carried out.The work of this thesis is divided into the following parts.（1）The structural framework of the three-mass block three-axis MEMS capacitive accelerometer is designed according to the performance parameters of the accelerometer.Firstly,the novel sensitive mass block structure is designed,then the elastic beam is selected,and the key component of the accelerometer,the elastic beam,is simulated and analyzed to analyze the influence of its structural parameters on the performance parameters,and the structural parameters of the elastic beam are determined in a comprehensive manner.Through the static analysis of the designed structure,the good overload resistance of the accelerometer is ensured.The X,Y and Z axial stresses under2000 g acceleration are 193 MPa,193 MPa and 138 MPa respectively,which are much smaller than the ultimate stress of silicon material.The mechanical sensitivity of the horizontal axial detection structure is 4.36 nm/g,and the mechanical sensitivity of the vertical axial detection structure is 4.93 nm/g.The modal analysis of the structure shows that the structure achieves modal separation to avoid modal interference,and the cross-sensitivity is less than 0.3%,which satisfies the design requirements.（2）In order to increase the application range of the accelerometer,this thesis also designed a high-precision three-axis MEMS capacitive accelerometer structure,which is characterized by a simple structure with a large range of ±50 g.When an acceleration of 2000 g is applied to the structure in the overload resistance analysis,the maximum stresses in the horizontal axis detection direction and the vertical axis direction are 370 MPa and 270 MPa,respectively.the structure has good linearity in the range The mechanical sensitivity of the structure was 54.67 nm/g and 92.93 nm/g in the horizontal and vertical axes,respectively,and the structure also achieves modal isolation with a cross-sensitivity of less than 1%,meeting the design requirements.（3）The L-edit software is used to draw the mask version of the three-mass block three-axis MEMS capacitive accelerometer with a range of ± 16 g designed in this paper,and the preliminary design of the accelerometer preparation process scheme is carried out. |
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