Research On Structure Design And Measurement Control Circuit Of Tunneling Magneto Resistance MEMS Gravity Sensor

The micro electro-mechanical system(MEMS)gravity sensor based on the tunneling magneto resistance(TMR)effect,with its extremely high sensitivity,small size and low power consumption,has gradually been paid attention by researchers in the field of high-precision gravity measurement equipment.In this paper,combined with the MEMS manufacturing process,the structure and detection circuit of the gravity sensor are designed,and the electrostatic force feedback closed-loop control technology is studied.The main research contents and related conclusions are as follows:(1)The advantages of TMR are analyzed and the principle of TMR effect is explained.The basic mechanical model of TMR gravity sensor is constructed,and the principle of magnetic field generation and gravity acceleration signal detection of TMR gravity sensor are studied.(2)The structure of TMR gravity sensor is designed.The structural design,working principle and overall structural characteristics of each part of TMR gravity sensor are analyzed in detail;static and modal simulation analysis of sensitive mass are carried out by ANSYS to optimize the structural parameters of the connecting beam;electromagnetic simulation analysis on the lower substrate assembly is performed by Maxwell to determine when TMR gravity sensor reaches a good working state;the relationship model between the magnetic field strength around TMR and the input acceleration is established.According to the simulation results,the range of TMR gravity sensor is 2g,and the sensitivity is 5.413?m/g.(3)Based on the structure and detection principle of TMR gravity sensor,a signal detection circuit scheme is designed.Aiming at the problem of environmental magnetic interference,a high-frequency pulsed magnetic field modulation method is proposed,which is simulated and demonstrated by Maxwell;based on the high-frequency magnetic field pulse modulation method,the interface circuit,preamplifier circuit,and detection circuit are studied and designed,which is simulated by Multisim;the circuit performance is tested through the experiment.(4)Based on the structure of TMR gravity sensor,the working principle of the electrostatic force feedback closed-loop is studied,and the mechanical model of feedback control is established;the analog electrostatic force feedback control method is studied,the PI control circuit is designed and the electrostatic force feedback simulation model is established by Simulink and the system performance is analyzed;the digital electrostatic force feedback control method is studied,and the digital feedback control scheme is designed based on FPGA.The research work in this paper provides an implementation plan for the development of TMR gravity sensor,which has certain guiding significance for future related research.