Identification, position sensing, and control of an electrostatically-driven polysilicon microactuator

This paper describes the design, fabrication, position sensing, and control of an electrostatically driven microactuator. The polysilicon microactuator, together with an on-chip electronic buffer, were fabricated by the modular integration of CMOS and microstructure (MICS) technology. The microactuator has a linear dimension of 310 /spl mu/m/spl times/340 /spl mu/m/spl times/1.7 /spl mu/m and a "long throw" range of motion of /spl plusmn/4 /spl mu/m. The driving comb fingers of the microactuator can generate up to 0.3 /spl mu/N of electrostatic force, which is able to pull the suspended microactuator across the substrate at an acceleration of over 270 G's. The lateral position of the microactuator, relative to the substrate, is sensed by measuring the change of capacitance in the sensing comb fingers with a Kalman filtering scheme, which achieves a position estimation error covariance below 0.01 /spl mu/m RMS. A state-variable feedback loop operates at a closed loop bandwidth of over 11 kHz, and enables the microactuator to settle to a position step input command within 0.12 msec. The microactuator was packaged and tested. Experimental results are given.