Research On PWM Closed-loop Feedback Interface Circuit Of Capacitive Accelerometer Based On ARM

Accelerometers made by MEMS technology have the advantages of small size,high integration,and high reliability,and have gained extensive attention and research.This thesis studies the interface circuit of the sandwich accelerometer made by MEMS technology,and proposes an ARM-based capacitive accelerometer pulse width modulation signal(PWM)closed-loop feedback interface circuit.The major work of this thesis contains:1.The physical model and electrical model of the sandwich capacitive accelerometer are studied and analyzed,and the detection principle of the differential capacitive accelerometer is understood.On this basis,the open-loop detection interface circuit and the closed-loop detection interface circuit of the sandwich capacitor accelerometer are compared and analyzed.2.The overall system model of the closed-loop feedback sandwich accelerometer is analyzed,and then the closed-loop force feedback model of the sandwich accelerometer is analyzed;then the simulation model of the PWM closed-loop feedback interface circuit of the capacitive accelerometer is created in SIMULINK.The ideal simulation results verify the feasibility of the scheme3.The capacitive accelerometer PWM closed-loop feedback interface circuit is designed and fabricated which is mainly composed of a capacitor voltage conversion circuit,a sample-and-hold circuit,STM32 microcontroller module based on ARM Cortex-M3 core and a feedback control loop,and the feedback control is performed through a PID control algorithm.4.The PCB circuit is tested.The output form of the closed-loop interface circuit of the capacitive accelerometer is PWM wave with different duty ratio and filtered DC voltage.The output change of the PWM duty ratio is 16.9%/g,the sensitivity is 1.05V/g.