Development Of Detection Circuit For Resonance-force Balance Capacitive Three-axis Accelerometer

The micro-mechanical acceleration sensor has the advantages of small size,light weight,low cost and mass production.Therefore,the micro-mechanical acceleration sensor has a broad application prospect in the automotive,communications,biomedical,aerospace,aerospace and other fields.The development of high-performance MEMS accelerometers has become a research hotspot in the sensor field.In view of the fact that the detection mechanism of the current miniature threeaxis acceleration sensor is single,the research team proposes a three-axis accelerometer with a bulk micromachined single-mass based on the principle of resonance-force balance capacitance detection.The resonance beam is used to detect the in-plane X/Y axis acceleration,and the Z-axis acceleration is detected using the differential capacitance detection mechanism working in the force balance mode.The center of the proof mass is located in the neutral plane of the supportting beam,reducing the inversion of the proof mass due to in-plane acceleration,resulting in a smaller cross-axis sensitivity of the accelerometer.The main work of this thesis is to develop the detection circuit of the triaxial accelerometer,establish the accelerometer detection system,and test the performance parameters.Based on the previous work of the research group,this dissertation focuses on the following two aspects:(1)In order to improve the detection accuracy of resonant frequency,a periodic self-adjusting frequency meter based on FPGA was designed.The sensitivity and cross sensitivity of the accelerometer's in-plane acceleration were tested using the rotary indexing table and the rotary indexing table.(2)A mathematical model of the capacitance detection system for detecting the Z-axis acceleration was established.The open-loop characteristics and closed-loop characteristics of the system were simulated using Simulink.Based on this,a capacitance detection system testing circuit for detecting Z-axis acceleration was developed.The method of PI correction is used to optimize the amplitude-frequency characteristics of the system so that the system can meet the conditions of closed-loop stability.Finally,the force feedback is used to make the accelerometer work in the closed-loop force equilibrium state.The sensitivity of capacitance detection system in open-loop and closed-loop States is tested by gravity field inversion method.