Control of bulk driven ultrasonic surface micromachined resonator

Control of surface micromachines using external piezoelectric actuators is an attractive method to achieve low voltage, high power and CMOS compatible micromachine operation. In this paper we present IC-compatible system, using a PZT to actuate surface micromachines with optical feedback to control surface micromachines. In our experiment, the packaged device was tested in vacuum (∼300 mTorr) and air, while the PZT plate was swept with frequencies from 10 kHz to 2 MHz, at a drive voltage of 5 Vpp. A circuit was build to lock-in to the signal from the resonant frequency. The signal from the beam was amplified with a high bandwidth operational amplifier and filtered. The output from the filter is fed into a phase lock loop, which is used to drive the PZT. The amplitude of the vibration was controlled using by adjusting the loop gain.