CONTROL TUNING IN A CLOSED LOOP CAPACITIVE MEMS ACCELEROMETER

This paper presents the mechanism used to close the loop for a MEMS capacity accelerometer, not only in terms of mathematical modeling, but also in terms of numerical simulation. By using the linear model of the mathematical model, some analysis related to the system quality is performed in frequencies. Because of the great nonlinearities present in the system at the level of the capacitive transducer, to extend the utility of the accelerometer, we need to close its loop. In the case of the micro-accelerometers, an electrostatic force is usually used as feedback. To improve the dynamic characteristics of the accelerometer, the feedback voltage is taken from a controller mounted on the direct way of the accelerometer, after the phase sensitive demodulator. The controller type is established using the transfer function of the linearized system and is tuned by using various integral criteria, as the minimum error surface criteria Ziegler-Nichols, and Kaya-Scheib method. Finally, the dynamic performances of the closed loop accelerometer are tested and discussed for all criteria used in tuning.