The Matlab/Simulink modeling and numerical simulation of an analogue capacitive micro-accelerometer. Part 2: Closed loop

The paper describes the closing of the loop for an analogue capacitive micro-accelerometer. The accelerometer is mathematical modeled, the mathematical relation being expressed both in complex domain and in time. Through equations linearization are made appreciations relative to the system quality in frequencies domain. Because of the great nonlinearities present in system at the level of capacitive transducer, to extend the utilization domain of the accelerometer, we need to close his loop. In the micro-accelerometers case, as a feedback force usually is used an electrostatics force. To improve the dynamical characteristics of the accelerometer the feedback voltage is taking from a regulator mounted on the direct way of the accelcrometer, after demodulator. The regulator type is established using the transfer function of the linearized system. Also, his tuning is made using the minimum error surface criteria Ziegler-Nichols and the numerical simulation. Finally, the dynamical performances of the closed loop accelerometer are tested and discussed with respect to the performances of open loop accelerometer.