Research And Design Of Silicon Differential Capacitive Accelerometer

Micro machined inertial sensors are one of the most important groups of silicon based sensors. Different kinds of accelerometers have been developed and the capacitive accelerometers become more attractive than others because of their own special properties. They have high sensitive, good dc response and noise performance, low drift, low temperature sensitive, low-power dissipation, and a simple structure. Capacitive accelerometers have found many applications and became one of the examples of successful commercialization of MEMS technology.Following a brief introduction of operating principle, this paper focus on the structure design and the system level simulation of comb capacitive accelerometers.The frequency characteristic of microstructure is obtained through frequency analysis. The models of microstructure, open-loop system and closed-loop system are established separately, and have been implemented in MATLAB with SIMULINK. System stability and input-output characteristic is analyzed. The simulation results shows that resonant frequency and damping coefficient are both important parameters for capacitive accelerometer, the output voltage varies in proportion to the amount of acceleration experienced along its sensitive axis.Because of its good linearity and high sensitivity, differential capacitance is often used as the microstructure of capacitive accelerometer. The comb microstructure this paper designed and simulated are one of the most popular structure of differential capacitance.Using Finite-Element Analysis (FEA) software ANSYS, the static, the modal and the harmonic response analyses are performed to research capacitive accelerometer's performance. Static analysis is used to determine the displacements and strains. Modal analysis is used to calculate the natural frequencies and mode shapes of a structure. Harmonic analysis gives the system frequency response characteristics. Through these analyses, capacitive accelerometer's linearity, toughness, sensitivity, natural frequencies and frequency response are received.The microstructure comb accelerometer we designed has the following characteristic: measurement range of±70g, shock survivability over 5000g, frequency range of 0～2000Hz.