Abstract
Position feedback and closed loop control are very important for MEMS mirror owing to the fact that the amplitude-frequency response of MEMS mirror is very susceptible to ambient temperature. This work reports a capacitive feedback solution of electrostatic driven MEMS mirror. To avoid the feedthrough of high voltage driving signal, a pulse width modulation (PWM) driving signal with low duty cycle and a current to voltage converter sensing circuit are employed. To eliminate the crosstalk induced by feedthrough, the sensing circuit is switched on only when the PWM signal is periodically low or grounded, but switched off during the PWM rise, fall and on-state time. The relationship between the electric sensing signal and the rotation angle is mathematically modeled, analyzed and experimentally verified. As a result of this research, sensing signal detection during the low state time of PWM is proved to be feasible to eliminate the influence of the actuation feedthrough. The peak value and the time when the sensing signal turns from negative to positive can be used to measure the amplitude and phase of the MEMS mirror with a precision of 3.10 and 0.13 mrad, respectively.
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